chem237labmanual fall2012 r

CHEMISTRY 237

LAB MANUAL

University of Illinois at Urbana-Champaign Fall 2012

Prof. Steven C. Zimmerman

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TABLE OF CONTENTS Page No. Course Information 3 Schedule of Experiments and Readings 6 Procedures and Grading 7 Penalties for Laboratory Misconduct 9 Lab Notebook, Lab Reports and Product Sample 10 Sample Prelab 13 Lab Report Guidelines 16 Sample A-1. BAD Lab Report 18 Sample A-2. GOOD Lab Report 22 Laboratory Safety 25 Waste Disposal 35 Apparatus in Desk 38 Care of Laboratory Equipment 42 Protocol for Starting Lab and Laboratory Check-out 43 “How To” Illustrations 44-63

Obtain a Melting Point Range Test the pH of a Solution Use a Separatory Funnel Perform a Gravity Filtration Use the Rotary Evaporator Tare a Flask Perform TLC Analysis Set Up a Dean-Stark Trap Set Up a Simple Distillation Set Up a Fractional Distillation Load an IR Spectrum Take an IR Spectrum Set Up a Reflux Perform a Vacuum Filtration Set Up a Chromatography Column Select a Solvent for Recrystallization

NMR Sample Submission Instructions Characteristic IR Stretching Frequencies and NMR shifts MNovaLite NMR Instructions and Presenting NMR Data in Reports Experiment 1: Isolation of the Components of BC Powder

63 64 66 68

Experiment 2: Preparation of Synthetic Banana Oil Experiment 3: Identification of a Conjugated Diene in Eucalyptus Oil

74 78

Experiment 4: NMR (dry lab) 81 Experiment 5: Acetylation of Ferrocene 82 Experiment 6: An Unexpected Reaction of 2,3-dimethyl-2,3-butanediol Experiment 7: Multi-step Synthesis of Fragrances Experiment 8: Enolate Chemistry – Chalcone Derivatives

86 88 93

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CHEMISTRY 237 COURSE INFORMATION Fall 2012 Instructor: Prof. Steven C. Zimmerman

Office Location – 345 Roger Adams Laboratory Office Hours – Friday 4-5 pm Email: [email protected]

TA’s: Badea, Adina email: [email protected] Giovino, Marissa email: [email protected]

Kortman, Gregory email: [email protected] Seymour, Craig email: [email protected] Yousaf, Zain email: [email protected] Lecture: Mon. 3:00 PM – 3:50 PM 112 Chemistry Annex

Tues. 9:00 AM – 9:50 AM 100 Noyes Laboratory Laboratory: Section AB1 Tues. 8:00 AM – 11:50 AM 263 Noyes Laboratory Section AB2 Tues. 1:00 PM – 4:50 PM 263 Noyes Laboratory Section AB3 Wed. 1:00 PM – 4:50 PM 263 Noyes Laboratory Section AB4 Thurs. 8:00 AM – 11:50 AM 263 Noyes Laboratory Section AB5 Thurs. 1:00 PM – 4:50 PM 263 Noyes Laboratory

FOR ANY SECTION CHANGES OR TO DROP

SEE RANDY WILKEY; 250 Noyes Lab; Phone: 244-9350; e-mail: [email protected] Also, inform WebCT administrators; email: [email protected]

HOW TO SUCCEED

BE PREPARED!! Read the experiments in advance and come to lab ready to start. Familiarize yourself with the background information provided in recommended reading. WORK EFFICIENTLY!! Plan the optimal use of the laboratory period. ASK QUESTIONS!! Save yourself from preventable errors and lost time. The teaching assistants and I are here to help you.

REQUIRED MATERIALS

Lab Manual: The Chemistry 237 Lab Manual is being made available by email from the instructor and on the course Compass website.

Text: Operational Organic Chemistry. Lehman, J.W., 4th Ed., Pearson

Education, Inc., 2009. Usage Card: Purchase at Illini Union Bookstore (809 S. Wright Street, Champ.) Laboratory Goggles: Must be approved goggles. Safety glasses are not acceptable. Laboratory Coat: Purchase at IUB, TIS, or Follett’s. Aprons are not acceptable. Lab Notebook: Chemical Education Resources Notebook (ISBN: 0875402488)

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RECOMMENDED MATERIALS Reference: J.W. Zubrick The Organic Chem Lab Survival Manual – 7th Ed.

John Wiley & Sons 2003 (ISBN: 0471215201) Models: HGS Researcher Model Set – Organic Chemistry B

EXAMS Exams: Material on the examinations will be taken primarily from the

lectures, assigned readings, and experiments. Exam/Quiz Schedule: Exam 1: Oct. 22nd and Exam 2 Dec. 3rd, both in lecture Quiz 1: Sept. 24th and Quiz 2 Nov. 5th, both in lecture No make-up or conflict exams

GRADING The course grade is based on a 820 point scale. The points are earned by performance on the experiments (~55%) and quizzes/exams (~45%). The breakdown is as follows: Estimated Course Points: (Subject to change) Lab Reports ..........................................................400 TA Grade ...............................................................50 Quiz 1 .....................................................................35 Quiz 2 .....................................................................35 Exam 1 .................................................................150 Exam 2 .................................................................150 Total Points for the Course ..................................820 Experiments: 1............................................ Isolation of BC Powder 50 2............................................................... Banana Oil 50 3........................ Conjugated Diene in Eucalyptus Oil 50 4.......................................................... NMR (dry lab) 50 5.......................................... Acetylation of Ferrocene 50 6....................................... Unexpected Diol Reaction 50 7................................................ Multi-step Synthesis 50 8.............................................. Synthesis of Chalcone 50 ............................................................... Total Points: 400 Criteria for Determination of Final Letter Grades Historical grade distributions for CHEM 237 Curve and break points Improvement TA and instructor evaluations Academic Integrity University of Illinois academic integrity policies will be enforced! See the following website for further information: http://www.uiuc.edu/admin_manual/code/rule_33.html and the CHEM 237 lab manual for further details.

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CHEM 237 Fall 2012 *Reading assignments in Operational Organic Chemistry textbook listed with experiments

Week of Experiment Aug. 27 (week 1)

LAB: Check In and Begin Experiment 1 DUE: Appropriate Clothing

Sept. 3 (week 2)

LAB: Continue Experiment 1 Note – Because of Labor Day, no lecture this week. DUE: - Pre-lab for Experiment 1

Sept. 10 (week 3)

LAB: Finish Experiment 1 and Begin Experiment 2 DUE: Pre-lab for Experiment 2

Sept. 17 (week 4)

LAB: Finish Experiment 2 and Begin Experiment 3 DUE: Pre-lab for Experiment 3; Post-lab for Experiment 1

Sept. 24 (week 5)

LAB: Finish Experiment 3 DUE: Post-lab for Experiment 2

***Quiz 1*** in lecture during the week of Sept. 24th

Oct. 1 (week 6)

LAB: NMR Exercises A and B; work during lab period [Separate Handouts on Website] DUE: Post-lab for Experiment 3

Oct. 8 (week 7)

LAB: Begin Experiment 4 DUE: Pre-lab for Experiment 4

Oct. 15 (week 8)

LAB: Finish Experiment 4 and Begin Experiment 5 DUE: Pre-lab for Experiment 5

Oct. 22 (week 9)

LAB: Finish Experiment 5 DUE: Post-lab for Experiment 4

***Exam 1*** in lecture during the week of Oct. 22nd

Oct. 29 (week 10)

LAB: Begin Experiment 6 DUE: Pre-lab for Experiment 6; Post lab for Experiment 5

Nov. 5 (week 11)

LAB: Finish Experiment 6 ***Quiz 2*** in lecture during the week of Nov. 5th

Nov. 12 (week 12)

LAB: Begin Experiment 7 DUE: Pre-lab for Experiment 7; Post-lab for Experiment 6

Nov. 19 (week 13)

THANKSGIVING WEEK BREAK

Nov. 26 (week 14)

LAB: Finish Experiment 7 DUE: -

Dec. 3 (week 15)

LAB: CHECK OUT DUE: Post-lab for Experiment 7

***Exam 2*** in lecture during the week of Dec. 3rd

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General Information: Procedures and Grading Course Objectives

The aim of Chemistry 237 is to provide you with an opportunity to learn about the separation, purification, synthesis, and identification of organic compounds, as well as develop your critical thinking and problem-solving skills. The course consists of weekly laboratory sections which involve experiments designed to introduce you to a variety of experimental techniques. You are expected not only to perform the experiments in the laboratory, but also to understand the principles behind the experiments so that by the end of the course you will be able to carry out chemical synthesis and to determine the structure of unknown compounds. Questions at the end of each experiment have been designed to supplement the concepts learned and encourage critical thinking.

The final experiment will be a culmination of all you have learned during the semester. You will be given the structure of a compound. Utilizing all of the techniques and concepts you have learned, you will design the synthesis, purification, and characterization of the compound. During the final experiment, your TA will evaluate your performance in the lab and assign you a grade accordingly. Your TA grade will be based upon demonstration of techniques learned as well as critical thinking and problem-solving skills in the lab.

Laboratory Safety

Read carefully pages 14-30 in the textbook on laboratory safety. It is imperative for your own personal safety and for the safety of those around you that you be familiar with prudent practices and laboratory etiquette. In addition to the text, please read the sections on Safety and Emergency Facilities, Laboratory Safety Guidelines and Waste Disposal in the syllabus. It is your responsibility to be aware of potential dangers and proper measures.

The Experiments

Experiments will be performed only in your assigned laboratory section. The schedule for the semester assumes that you will come to the laboratory each week well prepared and that you will use your laboratory time efficiently. At some times you will need to work on two different experiments in one lab period. You must plan ahead. For example, you should wash the glassware needed for the preparation of isoamyl acetate the week before you begin that experiment to avoid wasting time waiting for glassware to dry when you could be carrying out the experiment. TAs have the instructor's authority to send any students out of lab who are not properly prepared for the lab. Lab time missed for this reason cannot be made up! In addition, students who are late to lab will be given one warning and will then lose 5 points for each subsequent late arrival.

The first time a technique is used it will be described in detail. Thereafter it will be presumed that you can use this technique without further detailed directions. To do this intelligently, you must acquire not only manipulative skill, but also judgment about what a given procedure accomplishes and when it should be used. You will be EXPECTED to become progressively independent of TA assistance as the course advances.

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Occasionally, "difficulties" arise in the experiments. If the difficulties are judged by the TA to be of a serious nature and beyond your control, he/she may authorize that you be given additional starting material and/or extra time. If you are responsible for the difficulty, a grade penalty (20%) will be assessed for extra starting material. You have four hours to complete your lab. You will be assessed a penalty of 5% of the grade for that experiment for every 5 minutes after your allotted time. You will not be allowed to work in any laboratory period other than your regularly assigned section unless you have written permission from the instructor and the agreement of the TA supervising your extra lab.

If you miss a lab period, you must provide the instructor with advance warning or explanation (school activity, illness, family emergency) to obtain permission to make up the lab.

Grading

TO GET CREDIT FOR THE COURSE YOU MUST COMPLETE ALL OF THE EXPERIMENTS.

Each experiment will be graded according to the scheme below. However, the point distribution will vary according to the characteristics of the experiment, products, and product data. Reports will be graded on completeness, organization, quality, and interpretation of physical data and spectra, as well as consistency and clarity of explanations and conclusions. Graded reports will be returned one week after the due date.

Academic integrity is essential for scientific credibility! University of Illinois Academic Integrity Policies will be enforced. Penalties for plagiarism, cheating, falsifying data, etc. will be assessed by the instructor and according to University policy. Penalties may range from a zero grade on an individual assignment to a failing grade for the course. See the following Web site for further information:

http://www.uiuc.edu/admin_manual/code/rule_33.html

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Penalties for Laboratory Misconduct in CHEM 237

(Fall Semester 2012) Misconduct Penalty

Tardy to lab Warning (1st time), then 5 pts. off of lab report

per 10 minutes past 1 hour (after 1 hour you will not be allowed to start experiment)

Unexcused absence Failing grade for the course

Excused absence (by instructor) No penalty – must make up lab, arrange with instructor

Late lab report 1-2 days late 2-7 days late >7 days late

15% of maximum value of lab report; 25% of maximum value of lab report;

not accepted – failing grade for the course

Failure to turn in any lab report Failing grade for the course

Additional chemical samples Warning (1st time), then 20% of maximum value of lab report

Duplicate NMR spectrum 10% of maximum value of lab report

Not finishing lab in allotted time 5% of max value of lab report for every 5 minutes after lab time expires

Not wearing goggles or lab coat 10 pts. off of lab report plus expelled from lab until wearing them; time cannot be made up

Failure to wear proper attire Sent out of lab until proper attire is worn

Improper waste disposal (including chemicals, gloves, paper)

Warning (1st time), then 5 pts. off lab report per offense

Improper dispensing of chemicals Warning (1st time), then 5 pts. off lab report per offense

Failure to close chemical bottles or carboy stopcocks Warning (1st time), then 5 pts. off lab report per offense

Improper glass disposal (including pipettes, vials, and capillary tubes )


Failure to turn off and unplug unused equipment Warning (1sttime), then 5 pts. off lab report per offense

Negligent chemical spills 10 pts. off lab report per offense

Failure to maintain workspace (chemicals, wet bench top or floor, trash found),


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Laboratory Notebooks, Lab Reports, and Product Sample

Notebook

A bound laboratory notebook is required. A suggested one is Laboratory Research Notebook, published by Stipes. It is critical that all pertinent information be recorded during the lab period in the notebook. This serves as the primary source of information for your reports (see below). Read pp. 837-842 in the textbook and see the Guidelines and Sample Page for Laboratory Notebooks (below) in the syllabus. Leave the first couple of pages in your notebook for its table of contents.

Prelab

As part of the advance preparation for each experiment, all students must hand in a pre-lab. The information for the pre-lab is to be recorded in your lab notebook and the yellow carbon copy sheets are to be handed in at the beginning of the lab period for that experiment (See attached Guidelines and Sample Prelab in the syllabus).

The pre-lab report must be handed in to your TA before starting material for the experiment will be issued. You will not be allowed to start the experiment until you have handed in a satisfactory pre-lab report. If the TA considers your pre-lab report insufficient, you will be required to fill in any missing information before you are allowed to continue with the experiment. COME TO LAB PREPARED!!

Lab Reports

The content of the lab report is described in the Guidelines as well as more detailed instructions at the end of each experiment. Two sample lab reports are also provided. The reports are to be submitted to the TA on the student's lab day one week after the completion of the lab. Late reports (up to 2 days) will be assessed a penalty of 15% of the value of the experiments. Reports turned in between 2 and 7 days late will be assessed a 25% penalty. No report will be accepted more than one week late.

Postlab Questions

In most cases an extra set of questions covering the reading material and the lab experiment will be handed out at the beginning of the experiment. Answers to these questions should be submitted along with the lab report and will be incorporated into the lab report grade. A thorough record of observations made during the experiment is essential to answering these questions.

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Infrared Spectra

All spectra should be submitted with the reports and be clearly labeled with: student name, section, spectrum number, experiment number, and compound structure. (See IR spectroscopy at the end of the syllabus)

NMR Spectra

All spectra should be submitted with the reports and be clearly labeled with: student name, NMR identification number, section, spectrum number, experiment number, and compound structure. (See Preparation of NMR samples at the end of the syllabus)

Product Sample:

All compounds made in this course are to be handed in with the lab report. They should be bottled (liquids require the insertion of a Teflon film liner in the bottle cap; ask your TA) and labeled with your name, section, contents, tare and weight of contents. Tare is the weight of the empty vial with the label, cap and liner.

Guidelines for Laboratory Notebooks

Before you begin each experiment, you must write the pre-lab information (also see more detailed guidelines included with each experiment) in your notebook and show the carbon copies (yellow sheets) to your TA. The carbon copies must be turned in with every lab report.

Pre-lab information:

Your pre-lab should contain everything you need to complete the experiment, including physical constants, procedure, tables to record your data, etc. Although this list is not exhaustive, you should at least have:

ü Title of experiment and date; ü Balanced equations for any chemical reactions that will occur; ü Mechanisms for any chemical reactions (separate from equations); ü Table of reagents and products with molecular formulae and molecular weight (see

example of pre-lab) ü All pertinent physical properties of solvents (density, boiling, point, etc.) ü Literature values for all pertinent physical constants for reagents and products in table

of reagents and products and include source(s) (Handbook of Chemistry and Physics, Merck Index, etc.);

ü Calculate the theoretical yield(s); ü Summarized procedure (fill in on left side of page only, leaving right side for

observations and procedural changes made during lab period); ü Draw tables for recording any data obtained during experiment.

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During the experiment:

ü Using short phrases, describe how you proceeded (on right side of page); ü Record all observations, paying close attention to: temperature changes, color

changes, evolution of gases, and appearance or dissolution of precipitates; ü Note special techniques, apparatus or procedures; ü Be sure to record all errors, mishaps or unexpected problems (this will help you

understand the final result of the experiment); ü Describe the methods employed for isolation of the products; ü Record a crude yield and some description of the material (Note: When recording a

yield, always include the mass or volume and the corresponding percent yield according to the theoretical yield);

ü Outline purification procedures. This is best done in table format: 1) crystallization: solvents, amounts, temperatures, melting points, weight, physical

state, and % recovery. 2) distillation: vapor temperature (boiling point), pressure, weight, physical state,

and % recovery. 3) chromatography: column size, adsorbent and amount, eluent, fraction number,

weight, physical state, and % recovery. 4) Record the yield and percent at final stage of purity.

ü Properly label your infrared and nuclear magnetic resonance spectra sequentially throughout the semester and keep a record of the labels of each spectrum in both the notebook and lab report (this way you will not confuse them);

ü Record any comments that will aid in the interpretation of the outcome of the experiment or how problems could have been avoided if the experiment were repeated.

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Lab Report Guidelines

Experiment Title

Introduction: This section states the purpose or the goal of the experiment. In your own words, describe what you believe this goal to be and briefly state how it was achieved.

Reaction(s)/Table of Reagents:

X + Y Z MW: amount:* moles: equiv.:** misc.:***

Include full structures for the balanced reaction equation. All structures must be drawn using ChemDoodle, ChemDraw or a similar program, and each student must draw his/her own figures. Molecular formulas are insufficient. Amounts of reagents in units of mass and/or volume as well as in moles/millimoles are required. *amounts can be either mass or volume **Equivalents are calculated for the starting materials based upon the limiting reagent ***Miscellaneous information includes boiling points, melting points, density, etc. Theoretical Yield: Calculate a yield for each step as well as an overall yield (both in moles and grams). Mechanism: This section is required if a reaction or series of reactions were carried out. All structures must be drawn using ChemDoodle, ChemDraw or a similar program, and each student must draw his/her own figures. Experimental Procedure: This section contains a detailed yet concise account of how the experiment was carried out as well as any observations made during the experiment. Use grammatically correct, complete sentences in the past tense. Passive voice should be used when describing work performed, i.e. “the solution was stirred,” rather than “I stirred the solution.” Results: This section is an organized presentation of the data and contains a clear and concise discussion of the results. All numerical data should be in table format. Discussion: Thoroughly discuss the ramifications of any observations and procedural changes, as well as any implications that can be drawn from the obtained data. Include a brief summarization of the overall results at the end of the discussion section. This section should be separate from the Results section. It is not necessary to restate the entire procedure as part of the discussion.

Name _________________________ Experiment No. __________________ Section ________________________ Date __________________________

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Postlab Questions: The answers to these questions are placed at the end of the lab report. Use grammatically correct, complete sentences where applicable. Any structures and mechanisms are drawn with ChemDraw. The reader should be able to understand what the question is asking by reading your answer. ChemDoodle structure drawing program is FREE for UIUC students thanks to support by the Department of Chemistry at the University of Illinois. For a copy navigate to: http://www.chem.illinois.edu/clcwebsite/ChemDoodle.html

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Sample Lab Report - A-1 (Example of a BAD Lab Report)

Synthesis of n-Butyl Acetate

Introduction:

In this lab Le Chatelier's principal will be used to drive a reaction, and the techniques of fractional and azeotropic distillation will be learned.

Reactions:

C2H4O2 + C4H10O C6H12O2 MW: 60.05 74.12 116.6 amount: 12.64mL 14.82 g moles: 0.22 0.20 equiv: 1.0 1.0 1.0

MW: 60.05 74.12 116.16 amount: 12.64 mL 14.82 g moles: 0.22 0.20 equiv: 1.0 1.0 1.0

Theoretical yield:

expect to obtain 100% butyl acetate.

Experimental procedure:

First period: Placed .20 mol n-butyl alcohol, .22 mol glacial acetic acid, 3 mL sulfuric acid, 20 mL hexane, and some boiling chips in a 100 mL round-bottom flask. Then I filled the side arm of the Dean Stark trap and put it on the round bottom. Placed a reflux condenser on the Dean Stark trap. Heat the flask until water stops collecting in the trap (3 hours). Then I let the flask cool. Transferred the contents of the flask and the trap to a separatory funnel, drained off the aqueous layer, and washed the organic layer twice with two 25 mL portions of water. Dried it with some anhydrous magnesium sulfate.

Second period: Purified the crude liquid by fractional distillation. The fraction distilling from 120-125 °C was nearly pure n-butyl acetate. Took an IR of it.

Name __________________________ Experiment No. ___________________ Section _________________________ Date ___________________________

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Results and discussion: 20.09 g (.17295 mol) of n-butyl acetate was obtained. This is an overall yield of 86.47555% from the .20 mol of n-butanol we started with. I would have gotten more, but I didn't get to let the reaction go the whole three hours (my TA made me stop after two). Also, the material in my reaction flask turned green (everyone else's turned pink or purple), so there was probably something wrong with my starting material. The boiling point of my product is 122.5 °C.

IR Data Peak Comment Strength 2973.3 Hydrocarbon Stretch Strong 2886.8 Hydrocarbon Stretch Strong

1763.5 Carbonyl derivatives -- cyclobutanone or phenol or ester Strong

1466.3 ? Medium 1373.2 Esters, Acids, Alcohols (bending) Medium 1239.8 Esters in range, 1250-1190 cm-1 Medium 1038.5 ? Weak

NMR data (ppm) Peak Pattern Integration Assignment 4.10 3 2.02 OCH2 2.05 1 3.11 CH3CO 1.60 Many 2.16 OCH2CH2 1.45 Many 1.92 OCH2CH2CH2 0.93 1 3.09 CH2CH3

n-Butyl acetate was prepared in 86.47555% yield by Fischer esterification. The reaction was driven by making use of Le Chatelier's principle. We used a Dean Stark trap to remove water as it formed; this kept the back reaction from occurring and thereby drove the reaction to the right. The Dean Stark trap worked because hexane and water boiled off as an azeotropic mixture. After they condensed, the water fell to the bottom of the trap and couldn't get back out. The hexane, being less dense, was able to return to the reaction flask. The n-butyl acetate was purified by fractional distillation; as the vapor traveled up the fractionating column, it continually re-condensed and re-vaporized, and this left impurities behind.

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Commentary (or why this is a bad report) Introduction:

1) Use past tense. Future tense was used in the prelab because the lab hadn't been done yet. Now that it has been done, past tense is appropriate.

2) Don't just give generalities- be specific about the reaction that was done (i.e., butyl acetate was prepared by Fischer esterification).

Reactions:

1) Give structures. Drawing them by hand is acceptable.

2) The equation must be balanced. Here, one of the products (water) is missing.

3) Report the actual amounts and moles started with, not the amounts listed in the syllabus.

Theoretical yield:

Report the amount expected in grams and moles.


1) Again, report the actual amounts started with.

2) Report the amounts as they were measured. For instance, the acetic acid was not measured out in moles- it was measured in grams or milliliters.

3) Use complete sentences.

4) Don't use first person (I, me, my, etc.). For example, "then I filled the side arm" should be phrased "the side arm was then filled."

5) Keep tenses consistent. Don't alternate between past and present tense.

6) Don't omit crucial details. With what was the side arm filled? Was the magnesium sulfate removed before fractional distillation? The criterion that should be kept in mind is reproducibility- can somebody unfamiliar with the lab reproduce what you did from what you've written?

7) Phrase your sentences unambiguously. For example, washing the organic layer "twice with two 25 mL portions of water" can be read two ways.

8) Report the temperatures over which material was actually collected, not the ballpark range from the syllabus. If the range you collected over exactly matches that in the syllabus, make it clear that you are reporting your actual data. The overall problem with

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the procedure as written is that it is a restatement of the recipe in the syllabus. It should instead be a description of what you actually did.

The overall problem with the procedure as written is that it is a restatement of the recipe in the syllabus. In should instead be a description of what you actually did.

Results and Discussion:

1) Do not start sentences with numbers.

2) Report data in tables- don't bury it in text. This is especially important when more than one product is obtained (the extraction lab, for instance).

3) Calculate the percentage yield from the amount you started with, not the amount from the syllabus.

4) Be careful with significant figures. Percentages should be rounded to the nearest whole number.

5) Reaction times, color changes, and other conditions and observations should be reported in the procedure section. (Discussion of their ramifications is appropriate for the results & discussion section.)

6) Boiling (and melting) points should be reported as ranges.

7) In interpreting IR data, don't just copy the listings in the book or handouts. Also, be sure to report the type of bond that the signal correlates to. IR spectroscopy does not give functional groups, only a motion of a type of bond.

8) In interpreting the NMR data, use the correct nomenclature for peak pattern assignments, and peak integration values should be estimated to the nearest integer. Also, always draw a complete structure above the NMR table to make interpretation and assignments clearer to the reader.

9) The discussion should include not only how and why the results were obtained, but what implications can be drawn from the data.

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Sample Lab Report - A-2 (Example of a Good Lab Report)

Name ___________________________ Experiment No. ____________________ Section __________________________ Date ____________________________

Synthesis of n-Butyl Acetate

Introduction:

n-Butyl acetate was prepared from butanol and acetic acid by Fischer esterification. Azeotropic distillation was used to remove water from the reaction and drive the equilibrium. The product was purified by fractional distillation.

Reactions:

MW: 60.65 74.12 116.16 18.0 amount: 13.1 mL 15.19 g. 23.8 3.69 moles: 0.229 0.205 0.205 0.205 equiv. 1.1 1 1 1 BP (oC) 117-118 116-118 124-126 100 Density (g/mL) 1.049 0.81 0.88 1.00

Mechanism:


Glacial acetic acid (13.1 mL, 0.229 mol), n-butanol (15.19 g, 0.205 mol), hexane (21.1 mL), and sulfuric

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acid (3.0 mL) were combined in a 100-mL round-bottomed flask. A few Teflon boiling chips were added. The side arm of a Dean Stark trap was filled with hexane, and the trap was fitted onto the flask. A reflux condenser was attached to the trap. The mixture was heated to reflux for 2 hours, during which time it turned green. Due to time constraints, the reaction was discontinued before the expected amount of water had collected in the trap. The mixture was then allowed to cool to room temperature. The contents of the flask and trap were transferred to a separatory funnel and the green aqueous (lower) phase was removed. The organic phase was washed twice with 25-mL portions of water and dried over magnesium sulfate. The liquid was decanted and stored in a 100-mL round-bottomed flask.

Fractional distillation of the organic material was performed one week later. Two fractions were collected; distillation was discontinued when about 0.5 mL of material remained in the still pot. The first fraction (12.72 g, bp 58- 72 °C) smelled of hexane. The second fraction (20.09g, bp 122- 126 °C) had a fruity odor and was tentatively identified as n-butyl acetate. An FTIR spectrum was taken of the second fraction (neat).

Results:

n-Butyl acetate:

Theoretical Yield Actual Yield Percentage Yield Boiling Point 23.81 g. 20.09 g. 84% 122-126°C

IR Data Table

1H-NMR Data Table

IR data: Peak (cm-1) Comment Bond Type 2973 Strong sp3 C-H stretch 2886 Strong sp3 C-H stretch 1763 Strong C=O stretch 1373 Medium C-O stretch 1239 Medium C-O stretch

NMR data Chemical Shift(ppm) Peak Pattern Integration Coupling (Hz) Assignment

4.10 Triplet 2 2.1 OCH2 (d) 2.05 Singlet 3 -- CH3CO (e) 1.60 Multiplet 2 -- OCH2CH2 (c) 1.45 Multiplet 2 -- OCH2CH2 (b) 0.93 Triplet 3 2.1 CH2CH3 (a)

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GC Chromatogram Data Table

compound RT Area % area % of sample (by mass)

Sulfuric acid 2.097 2498 3.473

3 Butyl alcohol 2.289 8415 11.701

12 n-Butyl acetate 2.700 61002 84.825

85 (NOTE: PROPERLY LABELED SPECTRA SHOULD ALSO BE APPENDED TO THE LAB REPORT) Discussion n-Butyl acetate was obtained in good yield (84 %) by making use of Le Chatelier's principle. Water was azeotropically removed as it formed and trapped in the Dean Stark apparatus; removal of water prevented back reaction from occurring, and the equilibrium was thereby driven toward product formation. The boiling point of the product compares well with the literature value of 124 - 126 °C (Handbook of Chemistry and Physics, CRC Press, 76th Ed, 1995); this indicates that the product was reasonably pure. This purity resulted from fractional distillation- the fractionating column provided a means for vapor to condense and revaporize repeatedly, and thereby enhanced separation of mixture components. Product was lost in two ways. First, time constraints made it necessary to discontinue the reaction before completion; some of the starting material remained unreacted. Second, a small amount of material had to be left in the still pot when the fractional distillation was discontinued. This was necessary to prevent the pot from shattering. The color change during the reaction probably resulted from action of sulfuric acid on trace impurities; the effect on yield was minimal. POSTLAB QUESTIONS:

1) All questions are to be answered in complete sentence form. 2) Any structures and mechanisms should be drawn with appropriate software, not by hand (ChemDraw,

ISIS, etc.)

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Laboratory Safety

Read the section of the textbook on Safety before coming to your first laboratory session. You will fill out the Safety-device Location Worksheet during your first laboratory session. The importance of safety precautions in a Chemistry laboratory cannot be overemphasized. The following safety rules must be followed. Use common sense when working with chemicals and laboratory apparatus. As safety is an integral part of this course, your TA will be grading your compliance with these safety rules. Laboratory Safety Rules

1. You must NOT be in the laboratory without a TA present. The laboratory sessions are four hours in length. You will not be allowed in lab after your lab session has ended.

2. Safety goggles for eye protection must be worn properly in the laboratory at all times. If you need to remove your goggles, step outside the laboratory to do so. Prescription eyeglasses (even with safety lenses) do not provide adequate eye protection, especially from the sides. Therefore, you will be removed from the laboratory if you are found without safety goggles covering your eyes. If wearing contact lenses, appropriate eye protection must also be worn. It has been determined that wearing contact lenses in the lab does not present any greater risk than the naked eye. Contact lenses do not provide any protection from chemical splashing. Therefore, eye protection must be worn. When use of the eyewash is necessary, contact lenses must be removed since they prevent adequate and thorough flushing of chemicals from the eyes. It is advisable to inform co-workers that you wear contact lenses. This will help insure that proper safety measures can be taken in the event of an emergency.

3. A lab coat must be worn properly at all times while in the laboratory.

4. Closed-toed shoes that completely cover the foot MUST be worn in the laboratory at all times. Sandals or perforated shoes are not permitted, as broken glass and spilled chemicals are constant hazards.

5. Shorts and short skirts (above the ankle) will NOT be allowed. Shirts/blouses should protect the upper body. Loose clothing should not be worn. Do not wear hosiery as it will “melt” upon contact with acid and some chemicals.

6. You MUST note the location of the fire extinguishers, safety showers, eyewashes, and first-aid kits in the laboratory, so that you will know where to obtain these items if they are needed. You will fill out the Safety-device Location Worksheet during your first laboratory session.

7. Many of the chemicals used in the laboratory experiments will be new to you. You should become acquainted with the properties of every new chemical you use. The Merck Index or CRC Handbook of Chemistry and Physics and www.chemfinder.com are good sources for finding the properties and toxicities of many organic compounds.

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Access to material safety data sheets through various web sites can be obtained on the School of Chemical Sciences Safety Resources Web Page at http://safety.scs.uiuc.edu. All chemicals should be treated as though they are toxic. Compounds can enter the body by being absorbed through the skin, or by being inhaled or ingested. Therefore,

(a) Keep vessels covered. Put the caps back on the solvent bottles immediately. Never evaporate solvents other than water into the atmosphere. Wipe up any spills immediately. In order to check for odor, hold the sample about a foot away from your face and gently fan the vapors towards your nose. Do not put anything in your mouth. (b) You should use the gloves that are available. Keep your hood clean! DO NOT rub your eyes or your face without first washing your hands. If something does get into your eyes, remember to wash your eyes with plenty of water and notify your TA. You should protect your clothing by wearing a lab coat. Always wash your hands thoroughly before leaving the laboratory session. If you have any cuts or scrapes, cover them with band-aids, etc., before coming to the laboratory. Never handle door knobs, elevator buttons, water fountains, etc. with gloved hands as you could potentially contaminate these items.

(c) To dilute acids, carefully and slowly add the concentrated acid to the water, never the other way around. This avoids dangerous splattering. “Do like you ought to, add acid to water”.

8. Never heat a closed system! Always use boiling chips when heating any liquid, even water. When heating a test tube, never point it at yourself or at anyone else. Hot plates/stirrers pose a significant burn hazard. Flammable vapors can ignite when exposed to hot plates. Keep open solvent containers as far away from the hot plates as possible, while remaining in the ventilated work station. Keep papers and all combustibles away from the hot plate. Turn off the hot plate when not in use. Hot plates and aluminum heating blocks will remain hot for a long period of time after being turned off. Neither hot plates nor the aluminum heating blocks give any visual indication that they are hot, so check by holding your hand a couple of inches away while “feeling” for heat. Only after checking this way should you attempt to pick up the aluminum heating block or hot plate. If in doubt, use tongs. Do not wear garments with loose floppy sleeves or wrist cuffs while heating with the hot plate/aluminum block.

9. Do not use cracked or chipped glassware. Examine your glassware for “star” cracks. Broken glassware should be replaced immediately with new glassware from the storeroom. Do not handle broken glass with your hands. Sweep it up, or use a piece of toweling to grasp the pieces. The storeroom has leather gloves to wear while cleaning up broken glassware.

10. No waste products should be discarded down the drain. Properly labeled waste containers have been provided in the laboratory. If you have any questions as to where your wastes should go, ask your TA or a storekeeper.

11. In the case of an accident (cuts, burns, reaction to a chemical, etc.), inform your TA immediately. A limited degree of first-aid is available at the TA desk in the lab. If you are seriously injured, emergency services will be contacted (9-911) and you will be taken to the medical center. Report all accidents immediately. Your health is more important than your grade in Chem 237!

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12. Never pour chemicals directly from the storage containers directly into your reaction vessel.

13. Smoking, eating, and drinking are not permitted in the laboratory. Do not bring food or beverages into the laboratory.

14. No pets are allowed in the laboratory.

15. No “horseplay” is allowed in the laboratory.

16. No radios, CD players, iPODS or any other electronic device for playing music can be used while you are in the laboratory. No headphones or ear buds of any sort are allowed to be worn during lab.

A good perception of your surroundings is very important in a chemical laboratory. This state of mind requires your full attention. Take care of yourself and your neighbors. Immediately warn your neighbor if you see him/her doing something dangerous. It is natural for you to feel somewhat confused at times. Do not hesitate to ask your TA or the support staff for guidance with the use of the laboratory equipment or for advice on safety matters. Please respect the fact that other students must use the common laboratory equipment, such as the balances, melting point apparatuses, hoods, etc. Take care of this equipment, and clean up your messes immediately.

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Safety

The Chemistry 237 laboratory sessions will be held in 263 Noyes Laboratory. This lab contains the following safety and emergency equipment:

Drench hose/eye wash used for chemical splash

or debris in the eye.

Eyewash/drench hose is

activated by pulling paddle lever forward.

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Eyewash/drench hose can

also be pulled out of bench to rinse extremities.

When using eyewash, hold eye open to ensure

proper flushing.

Eyes should be flushed for a minimum of 15

minutes per eye.

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Safety showers are located in each laboratory

bay as well as in the chemical dispensing area. Showers are indicated by a large yellow square on

the floor.

Shower curtains are provided at shower

locations for privacy while disrobing.

Curtain should be pulled around while entering the

safety shower.

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Safety showers are activated by pulling the wall mounted handle out

and down.

Fire extinguishers are located throughout the

lab.

To use the fire extinguisher first remove the seal by twisting and

pulling.

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Next, pull the safety pin

to remove.

Raise the horn and point it at the base of the fire

while squeezing the trigger/handle. Sweep the base of the fire with the

extinguishing media until out. Back away to avoid

flash back.

If unsure of your ability

to fight a fire, or if the fire is too large to safely

extinguish, activate the fire alarm by pulling the

fire alarm box lever.

The fire alarm is located in the hallway by the

stairs.

Safety Safety Device Location Worksheet See Safety Device Location worksheet on next page. You will need to fill this out and keep it for your reference. Appropriate clothing You must wear appropriate clothing in the laboratory at all times. You MUST wear your safety goggles over your eyes at all times in the laboratory! DO NOT wear loose or skimpy clothing (saris, neckties, shorts, halter tops, overly large or ragged laboratory coats). DO wear closed shoes in the lab. DO NOT wear sandals or perforated shoes. Long hair must be tied back.

For additional laboratory safety information and resources, access the School of Chemical Sciences Web site page at http://safety.scs.uiuc.edu

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Safety-Device Location Worksheet Chemistry 237

Name: _________________________ Lab Section: ____________ Date: ____________ Before you begin laboratory work in this course, you must be familiar with the location of the safety devices on the diagram of the lab shown below. Use these symbols:

Quantity Equipment Symbol Quantity Equipment Symbol Eye-Wash Faucets X Exits

Overhead Showers Fire Extinguishers First-Aid Box Fire Alarms (in the hallway)

Stairs Entrance to Chem 237 Lab Indicate your assigned work area, and then indicate with an *asterisk* the nearest eye-wash faucet, overhead shower, fire extinguisher, fire alarm, and two exits. Give the completed Safety-Device Worksheet to your TA before starting laboratory work.

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Waste Disposal All chemical waste must be placed in appropriate containers in the lab. All containers must be kept closed when not actively adding waste.

All contaminated

glassware must be put

in the containers

located on the floor through-

out the lab.

Glassware goes in the

white container. The white

containers are for broken

glass or used scintillation

vials.

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Pipettes and

capillary tubes go in

the red container.

Solid organic waste should be put in the containers

located in the hood.

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Organic liquids should be placed in

the containers in the hood.

The label on the container indicates the compounds that can be put in it.

There is a different

container for each

experiment.

Gloves, paper towels, filter

paper and weighing

paper go in the yellow containers. The yellow

containers are for

chemically contaminated

non-glass waste.

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Apparatus in Desk Description Amount Picture

Adapter, distilling #14/20 w/ 10/18 1

Adapter, vacuum bent #14/20 1

Beaker, Griffen w/spout 50-mL 2

Beaker, Griffen w/spout 100- mL 2 Beaker, Griffen w/spout 150-mL 2 Beaker, Griffen w/spout 250-mL 2

Beaker, Griffen w/spout 400-mL 2

Bottle, polyethylene wash 250-mL 1

Brush, test tube, small 1

Clamp, hose spring 4

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Clamp, plastic yellow, #14/20 4

Condenser, Liebig #14/20 1

Cork Ring, 100-mL, #2 1

Cylinder, graduated, 10-mL 1

Cylinder, graduated, 100-mL 1

Distillation column #14/20 1

Filter adapter, neoprene #2 1

Filter adapter, neoprene #3 1

Flask, Erlenmeyer, 25-mL 2

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Flask, Filter, 50-mL 1



Flask, round bottom #14/20, 25-mL 2



Flask, round bottom #14/20, 250- mL 1

Funnel, Buchner, polyethylene 55 mm 1

Funnel, powder polyethylene 70 mm 1

Funnel, powder glass 70 mm/ with 14/20 joint 1

Funnel separatory Squibb 125-mL (with stopcock and stopper) 1

Funnel separatory Squibb 250-mL (with stopcock and stopper) 1

Glass Rod, 8" 2

Policeman, rubber 2

Rubber bulbs, 2-mL 2

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Sodium chloride discs (25x5 mm) in a jar containing white and blue dessicant. If the discs are hazy/chipped, or if the dessicant is white and purple, see the TA.

2

Spatulas, steel, 2 blade 1

Sponge 1

Stir bar, Fischer brand egg-shape 1 Stopper, plastic, #14/20 1

Test tubes 18x150 mm 15

Test tube holder 1

Tongs, Crucible, 9" 1

Tube, drying straight Poly 6 in. 1

Watch Glass 1

Wax pencil 1

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Care of Laboratory Equipment -- General Guidelines Care of Hot Plates

(1) Always plug the hot plate into a wall outlet. (2) Never place an empty flask on a hot plate. (3) The porcelain top of the hot plate should be kept clean. (4) Never place a container of ether on a hot plate--this is a significant fire hazard.

(5) Remove round-bottom flasks from the heat source immediately after heating is complete.

Care of Balances

(1) Never weigh directly on the balance pan. Always use the weighing paper provided. (2) Promptly clean up any chemicals you spill on or around the balance. (3) Note: The balances weigh to either ±0.1 or ±0.01 grams.

Care of Melting Point Apparatus

(1) Do not take the temperature above 220 °C without the permission of the TA. (2) Do not break the m.p. capillaries in the apparatus. If a capillary is broken in the apparatus, please alert the TA. (3) Make sure the m.p. apparatus is OFF when you are done. (4) Note: corrections are noted on each thermometer.

Care of Infrared Spectrometers (IR)

(1) Each student should close his/her computer IR window after use. (2) Do not wear gloves while using IR.

Care of NMR Tubes (NMR)

(1) NMR Tubes are fragile and expensive, treat them accordingly. (2) Be particularly careful when fixing and removing the cap. (3) Pour the contents of the NMR tube into the designated disposal container. (4) Rinse the inside of the tube repeatedly (4 or 5 times) with acetone. (5) Allow ample time for the tube to dry before preparing your next sample. Be sure that your sample tube is free of any traces of organic residue and wash solvents (such as acetone, hexanes, etc.)

Care of NaCl Plates

(1) Clean your plates after every use with acetone.

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PRIOR TO THE FIRST LAB PERIOD

1. Looking over and printing the Chem 237 syllabus is highly recommended. Or, find your syllabus on the course Web site. Bring your bound syllabus to lab. 2. Purchase the textbook "Operational Organic Chemistry" (John W. Lehman) at the bookstore. 3. Purchase your Usage Card at the Illini Union Bookstore. This must be turned in no later than the beginning of the second lab period or you will not be allowed to begin that week’s experiment.

4. Make sure to have safety goggles (not safety glasses), a lab coat, and a bound laboratory notebook (with carbon copies) for the first lab period. All of these items can be purchased at the Illini Union Bookstore.

5. Read the entire experiment in the syllabus and the designated pages in the textbook.

6. Prepare the prelab according to the instructions in the experiment and guidelines and examples in the syllabus.

DURING THE FIRST LAB PERIOD

(CHECK-IN/STARTING THE FIRST EXPERIMENT)

1. Go to 263 Noyes Laboratory and obtain your lab drawer assignment, personal information card, and lock combination card from your TA. Once filled out, return the lock combination card, personal information card, and usage card (if you have it already) to your TA.

2. Bring equipment to lab: lab notebook, goggles, lab coat, and usage card.

3. Verify the contents of your drawer against the inventory in the syllabus (pg.37-40).

4. Replace any broken or missing items from your TA.

5. Complete the Safety Facilities Test and hand it in to your TA.

6. Hand in your PRELAB to your TA at the beginning of the lab period to obtain the starting materials.

7. During the prelab lecture, you will be shown how to use two important pieces of equipment in the lab: the balance and the melting point apparatus.

8. Begin experiment 1. By the end of the lab period, you should be able to isolate the three compounds.

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PROTOCOL FOR CHECKING OUT (LAST LAB PERIOD)

1. Thoroughly clean all of your glassware and equipment. 2. Lay out the glassware in your hood in the order they appear in the inventory. 3. Check the inventory of your equipment against the master list in the Syllabus. 4. Replace any missing, chipped, cracked, or broken item(s).

5. When the inventory is complete, have a Teaching Assistant check the desk contents. He/She will put the items back in the desk as they are checked off. 6. Once you leave the lab, you may not return. Be sure you have all of the information you need. 7. Remember to submit your final Lab Report before the deadline!

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The “How To” Illustrations It can be difficult learning to perform a new task, especially when you are completely unfamiliar with the apparatus involved. In this section, a few illustrations are provided for various techniques you will use throughout the semester. Feel free to refer to this section as often as you like, but you should strive for mastery of the technique as soon as possible, so you can use your time in lab more efficiently.

How to Obtain a Melting Point Range Place a small amount of the solid on a watch glass. Obtain a melting point capillary tube (sealed on one end). Gently tap the open end of the capillary tube 2-3 times into the solid until a small amount of the solid is collected in the end of the tube.

Turn the tube and gently tap the closed end onto the bench surface until the solid falls down into the bottom of the tube. Alternatively, drop the capillary tube (closed end down!) through a piece of hollow glass tubing placed vertically on the bench top.

Repeat the steps above as needed to obtain approximately 1 mm of solid in the bottom of the capillary tube. Do not load too much sample in the tube, as it will take longer to melt and cause a broader melting point range.

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The melting point apparatus will look similar to the apparatus on the right. The Mel-Temp is attached to a digital thermometer which will be on the bench next to the apparatus. Turning the black knob clockwise will increase the temperature, but the numbers on the dial do not directly correspond to the temperature. The sample is loaded into the chamber behind the magnifying lens. When obtaining a melting point range, be careful that you do not heat the sample too quickly. The thermometer does not register temperature changes instantaneously, so if you are heating too fast, it will seem that your sample has a lower melting point than it should. It should take around 30-60 seconds for a sample to melt completely.

The best way to accurately determine a melting point is to prepare two samples: the first one is run quickly to find the approximate melting point range; the second one is run more slowly to get more accurate results. This is much easier and faster than running one sample very slowly to avoid overshooting the temperature.

How to Test the pH of a Solution Obtain a 2-inch strip of pH paper. Make sure your gloves are clean (even water will render the pH paper useless). Tear the pH paper into little pieces and place them onto a paper towel. Remove a drop from the solution you are testing with a pipette and drop onto the paper. Never dip the paper into the solution! There are chemicals on the paper which could contaminate your product. Use the color guide on the side of the bottle to determine the pH.

46

How to Use a Separatory Funnel Set up an iron ring on a ringstand to hold the separatory funnel. Make sure it is tightly clamped so the funnel does not fall. Close the stopcock and place a beaker under the funnel before adding any liquids. Always have a container under the funnel, just in case you forget to close the stopcock!

Place a stopper in the top of the funnel. Wrap your index and middle fingers tightly around the stopper to prevent it from falling out while you are shaking the contents. Invert the funnel and shake.

While you are shaking, pressure will build up inside the funnel, especially if there is a neutralization occurring (such as with sodium bicarbonate washes). Make sure to vent the funnel often to prevent too much pressure buildup.

With the funnel inverted, open the stopcock. You may hear a loud hissing as the gas is released. Continue shaking and venting until gas is no longer released. Remember to close the stopcock before turning the funnel upright. Return the funnel to the ring as in the first picture. Remove the stopper before draining the solution, to prevent a vacuum from forming in the funnel.

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How to Perform a Gravity Filtration Set up a glass funnel as pictured on the right. Obtain a piece of filter paper (11”) and fold it up so that it fits into the funnel. Wet the paper with the solvent you are using before you pour the solution through the funnel (for example, if your solution contains methylene chloride, you should wet the paper with that).

Pour the solution into the paper, making sure that you do not fill the funnel too quickly, causing overflow. If you are filtering a hot solution, place the flask back on the heat source while you are waiting to keep the solution hot. If you are going to evaporate the solution after filtering, you should filter into a tared round bottom flask (see How to Tare a Flask).

How to Use the Rotary Evaporator Locate the rotary evaporator closest to your workstation. There are several distributed throughout the lab.

DO NOT use the rotary evaporator until there is dry ice in the cold finger. If there is no

dry ice in the cold finger when you need to use it, ask your TA to add some.

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Attach your flask to the ground glass joint on the apparatus. Be sure to place a yellow clamp on the joint to prevent the flask from falling into the water bath. The smaller part of the clamp goes around the top of the joint.

Locate the red power switch just below the apparatus on the bench. This will turn on the power to the evaporator and the vacuum pump below the bench.

Switch on the rotor by flipping the green switch located on the upper part of the evaporator. The speed of rotation is controlled by turning the black knob clockwise.

To begin evaporation, locate the two valves on the side of the cold finger trap. The two way valve (the top valve) should be pointing toward the vacuum line, and the pressure release valve (the bottom valve) should be closed (as shown on the right).

If the solvent you are evaporating has a higher boiling point, you may need to heat the solution. The switch for the water bath is located on the lower left of the apparatus.

When you are done with the evaporator, be sure to open the pressure release valve, turn off the rotation, and turn off the main power switch before removing your sample.

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How to Tare a Flask To tare a flask simply means to preweigh the empty flask. You can then determine the mass of product by weighing the flask containing the product and subtracting the tare value. First check that the balance is set to zero by pressing the blue tare button. If you are going to tare a round bottom flask, first place a cork ring on the balance, then zero the balance.

Place the flask on the balance and wait for the digital readout to stop fluctuating. Record the mass of the empty flask in your notebook.

Using a sharpie or permanent marker, write the mass on the side of the flask. Be sure to label the flask on the upper half so the numbers are not smeared during evaporation. You should also write some other identifying mark as well when working with multiple flasks to prevent confusion.

How to Perform TLC Analysis

Obtain a silica gel plate. Notice that one side is smooth while the other side is coated with silica. The side coated with silica is the one you will be using. Be careful when handling the plate or the silica may flake off. Lightly draw a line with a pencil 1 cm from the bottom of the plate, being careful not to scrape the silica surface off. This will serve as your baseline. Draw evenly spaced dots for the samples you will be testing. Label them so that you will remember which is which.

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Place a small amount of each compound you are testing in separate test tubes and add 5 drops of acetone. Since the best separations are achieved when this spot is as small as possible, the solution should be applied with a very small capillary tube. Place a 4-mm diameter spot of the mixture on each of the three narrow plates at the pencil mark. Be sure the spots are above the level of the solvent in the developing tank or they will dissolve in the solvent and give erroneous results.

Develop the TLC plates in a chamber like the one shown here using a beaker and aluminum foil. Place a half-circle of filter paper in the beaker to help increase the vapor pressure and consequently cause the plate to develop faster. Cover the bottom of the beaker with your eluent system (refer to procedure of your experiment). Remove the TLC plate when the solvent front is within 5 mm of the top of the plate. Mark the solvent front lightly with a pencil.

Allow the solvent to evaporate and place the plates under a UV light source (see TA for assistance). If the spots are not visible under UV light, place the plates in an iodine visualizing tank. With a pencil, lightly circle the spots on the plate. Make a drawing of the plate in your lab notebook and be sure to clearly label the origin and the solvent front as well as the location of the spots.

You should report Rf values for each compound in each solvent. Remember that when the mixture contains more than one compound, each will have its own Rf value. The Rf value is calculated by measuring the distance traveled by the compound (x) and dividing by the distance traveled by the solvent (y) from the baseline.

When you are using TLC to decide upon an eluent system for column chromatography, you should select the solvent system that results in the greatest difference in Rf values between the components in the mixture.

x

y

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How to Set Up a Dean-Stark Trap The apparatus for azeotropic distillation is shown to the right. The Dean-Stark trap is attached to the round bottom flask and is topped by a reflux condenser. As with any distillation, make sure the water hoses are secured with hose clips and that the ground glass joints are secured with yellow clamps (see How to Set Up a Simple Distillation for further instructions). Make sure water is flowing through the condenser before you begin heating.

Before you begin, you need to mark the sidearm of the Dean-Stark trap to let you know when the distillation is complete. Check your pre-lab for the calculated amount of water that will be generated during the reaction. Add that amount of hexanes to the sidearm. Mark this level with a rubber band or permanent marker. Once you have done this, fill the sidearm with hexanes and begin heating. Stop when the water level reaches the mark.

How to Set Up a Simple Distillation

The equipment you will need for a simple distillation is pictured above. In addition, you will need two water hoses long enough to reach the sink at your workstation. Make sure the round bottom flasks you use are sufficiently large enough to hold the reaction mixture or distillate. You should tare any flask that is used for collecting distillate (see How to Tare a Flask).

Water in

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Ground glass joints should be secured with yellow clamps to ensure a tight seal and prevent the apparatus from falling apart. The smaller half-circle of the clamp fits around the top part above the joint.

The thermometer needs to be positioned correctly to ensure proper measurement of the temperature of the vapor. The tip of the thermometer should be just below the bottom of the sidearm of the distilling adapter. This is the point where the vapor will be condensing and can be considered to be close to the boiling point of the liquid. All hoses must be secured with hose clips. This is to ensure that the water pressure does not pop the hose off the condenser. Press the clip onto the hose then pinch tightly to fold the shorter bent hook over the longer end. A correctly attached hose clip is shown to the right. Note how the shorter bent hook is hooked over the longer end.

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The completely assembled apparatus is shown to the right. Notice the location of the yellow clamps and hose clips. Make sure water is flowing in the condenser before you start heating. Water should flow in from the right side (or bottom) of the condenser and flow out through the left side (or top).

The flask for collecting the distillate should be placed in an ice bath, to help condense the vapors and prevent the liquid from evaporating.

Water in To sink

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How to Set Up a Fractional Distillation The fractional distillation apparatus is very similar to the simple distillation apparatus. The major difference is the addition of a distillation column between the stillpot (the round bottom flask on the aluminum heating block) and the distilling adapter. This column allows for greater separation of liquids with relatively close boiling points.

Once again, check to make sure your thermometer is positioned correctly. When distilling liquids with boiling points greater than 100°C, you should wrap the distilling column and distilling adapter in aluminum foil, to keep the glass from cooling and slowing down the distillation.

Distilling column

Water in

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How to Load an IR Spectrum

Remove sample cap.

Remove and clean (with acetone in the dry well) the sample holder

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Place salt plate on sample.

Replace sample cap and take the IR spectrum.

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How to Take an IR Spectrum 1. Follow on screen instructions.

2. Clear away any previous spectra. To do so, click Views, and clear all spectra. When it asks to save, click No and clear report.

3. Click Collect à Sample à Enter.

4.

If your spectrum is satisfactory, click Analyze à Find Peaks. By clicking above and below the “threshold” line, you can include or exclude peaks. When finished, click OK.

5. To print click File à Print à OK (in top right corner). Click Cancel after page 1 (then OK if an error window appears).

6. Collect printout and sample.

How to Set Up a Reflux A reflux apparatus is pictured on the right. Be sure to check the procedure for each experiment to determine whether you should heat with the aluminum heating block or with a hot water bath (a hot water bath can be made simply by filling a large beaker half full with water and placing on the hot plate). The still pot is connected to a condenser, which is in a vertical position instead of horizontal (as in the simple distillation apparatus).

Once again, ensure that all hoses are secured with hose clips and water is flowing through the condenser before you begin heating. Do not let the vapors escape through the top of the condenser! If the vapors climb too high, reduce the heat.

Water in

To sink

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How to Perform a Vacuum Filtration The vacuum filtration apparatus should never be hooked directly to the vacuum line at your workstation. It should be hooked to the vacuum trap provided for you. The hose from the vacuum flask is attached to the top of the vacuum trap. The hose on the side of the vacuum trap is hooked to the nozzle for the vacuum line. Be sure to clamp you filtration flask firmly to prevent it from toppling and spilling your product. Place the neoprene filter adapter in the mouth of the flask and insert the Büchner funnel into it.

Obtain a piece of filter paper (9”) and place inside the Büchner funnel. Turn on the vacuum and wet the paper with whatever solvent you are working with (for example, if you did a recrystallization with methanol, you should wet the filter with cold methanol). Pour the solution containing your solid onto the filter paper. Leave the solid under vacuum for several minutes to remove any remaining solvent.

To trap

To vacuum

From flask

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How to Set Up a Chromatography Column Two types of columns will be used in this course; either with a glass frit (pictured on the left) or without (shown on the right). Be sure to securely clamp the column and secure the ringstand to prevent it from falling over. Always have a container below the stopcock just in case the column leaks. Check the stopcock to make sure it is assembled correctly before proceeding (ask your TA for assistance).

For the columns without a glass frit, you must first pack cotton into the tip as shown in the top picture, and then add a small layer of sand with an even surface (pictured on the bottom).

Then for both types of column:

Close the stopcock and add several mL of your eluent to the column. Open the stopcock and allow most of it to drain out. Close the stopcock.

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Prepare your stationary phase by obtaining the recommended amount of alumina or silica gel in a large beaker. Add your solvent system to the solid and stir. You should add enough solid that the mixture becomes a slurry, like quicksand.

NOTE: It can be difficult to correctly form a slurry with alumina, as it is heavy and quickly settles back to the bottom of the beaker. You will need to stir rapidly and pour quickly to get the alumina slurry into the column. It may take more solvent to get all of the alumina into the column.

Once you have formed a slurry, quickly pour the mixture into the column and open the stopcock. Use your glass stirring rod to help direct the slurry into the column and prevent bubbles and cracking later.

If you are working with alumina, you will need more solvent to rinse the alumina down the sides of the column.

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Once you have a sufficient amount of your slurry in the column, pack the stationary phase by tapping the sides of the column with a rubber hose. If the solvent level is too low, add more solvent until all of the stationary phase has completely settled in the column (you should notice when you first add the slurry that the level of the stationary phase slowly drops; the stationary phase is packed when you no longer see this occurring).

Allow the solvent level to drop to just above the top of the stationary phase and close the stopcock. Add just enough sand to create a layer of several inches on top of the stationary phase. Drain the solvent to just below the top of the sand level and close the stopcock.

Dissolve the crude material in a small amount of the recommended solvent (save a small amount of the crude material for TLC analysis; refer to procedure for each experiment). Using a pipette, add the solution to the top of the column. Open the stopcock and allow the solvent to drain to just below the sand level and close the stopcock again. Add the eluent system slowly to the column, making sure to not disturb the crude material.

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Open the stopcock and begin collecting the fractions. Collect the eluting solvent as fractions in separate test tubes. Fill each test tube approximately ¾ of the way full. Swap to the next test tube as shown. To determine which test tubes contain the product, perform TLC analysis (see How to Perform TLC Analysis).

How to Select a Solvent for Recrystallization

Place a spatula-tip of the crude solid in a test tube and cover the solid with a few drops of the solvent you wish to test. Strike the tube gently to mix and note whether the crude solid dissolves. If it dissolves, that solvent is not suitable for recrystallization. If the crude solid does not dissolve, you can proceed to the next step.

Heat the test tube in a hot water bath until the solvent begins to boil. Point the tube away from you and shake it vigorously. Note whether the crude solid dissolves. If the solid dissolves, remove from heat and observe whether the solid reforms. If it does, the solvent is sufficient for recrystallization. Repeat this procedure with different solvents using small samples of the crude solid. Be sure to record your observations in your notebook.

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NMR Sample Submission Instructions

Follow instruction sheet in lab.

• For liquid samples, dip a micropipette (TLC spotter) into

your sample. Spot the liquid onto the filter.

• For solid samples, collect a small amount of sample in the tip of a Pasteur pipet. Transfer the sample to the filter, and

wipe off any excess material from the sides of the filter.

• Place the filter in the sample vial. Using a glass syringe, draw up 50 microliters (µL) of deuterated chloroform

(CDCl3). Carefully inject the solvent into the top of the filter. This will approximately fill the top of the filter.

• Tightly cap the vial. Place the vial in the centrifuge (always

balance the centrifuge!) and spin the vial for 1 minute.

• Wait until the centrifuge comes to a complete stop, and remove the vial from the centrifuge, maintaining the vial in

an upright position.

• Unscrew the cap, remove the filter using the filter removal tool, and replace the cap.

• Place the vial in the sample holder in the number

corresponding to your assigned hood number. • To clean the vial: Rinse with CHCl3 (not CDCl3) at the beginning of the lab period and allow to air-dry in the hood

during the lab period.

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Spectral Analysis-Infrared Spectroscopy-IR Stretching Frequencies

Group (cm2) Functional Group Comment

O-H, N-H 3700-3500 OH(non-hydrogen bonded) sharp

3500-3200 OH (hydrogen bonded) broad

3500-3300 N-H primary, two bands; secondary, one band

C-H 3200-3000 vinyl or phenyl C-H 3000-2800 alkane C-H 2750 aldehyde C-H

2300-2000

usually weak

1840-1800 anhydride two bands 1800 acid chloride

1770 cyclobutanone or enol ester

1740 cyclopentanone 1740-1725 acylic ester

1735-1720 aldehyde , at 2750 confirms

1725-1700 carboxylic acid , at 3300-2500 (broad) confirms

1710

1680

acyclic ketone, cyclohexanone,

phenyl ketone

1690-1640 amide 1690-1640 imine usually weak

1680-1640 alkene usually weak confirmatory

bands 1300-1100 esters in range 1250-1190

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1560-1540 -NO2 strong 1390-1360 -NO2 strong 970-960 trans alkene 700-650 cis alkene 1000-990 monosubstituted alkene 920-900 monosubstituted alkene 890-860 2,2-distributed alkene 800-700 alkyl chlorides 600-500 alkyl bromides

Common Impurities in NMR Samples:

Impurity Chemical Shift (in CDCl3) Multiplicity Assignment Water 1.56 ppm Singlet H2O Acetone 2.17 ppm Singlet CH3 Chloroform 7.26 ppm Singlet CH Dichloromethane 5.30 ppm Singlet CH2 Ethyl Acetate 2.05 ppm Singlet CH3CO 4.12 ppm Quartet CH2CH3 1.26 ppm Triplet CH2CH3 n-Hexane 0.88 ppm Triplet CH3 1.26 ppm Multiplet CH2 Methanol 3.49 ppm Singlet CH3

Note: For any other common solvents/impurities that may be in your sample, you can find the information in: J. Org. Chem., Vol. 62, No. 21, 1997, pg 7513.

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Link to MNovaLite Instructions To find instructions for using MNova Lite for NMR Data Analysis, please go to:

http://scs.illinois.edu/nmr/handouts/getting_started/MNovaLiteInstruct.pdf

Presenting NMR Data in CHEM 237 Lab Reports

1. Turn in the spectrum properly labeled: Your Name, Section letter, Exp #, Date, Compound name, and most important compound structure. Also always turn in a spectrum, which includes all peaks (full) from TMS at 0 ppm to at least chloroform at 7.26 ppm. Of course if you have peaks beyond chloroform include them.

2. In results section report the NMR data in a table format with a labeled structure shown above the table.

NMR Table for n-Butyl Acetate

O

O

a

b

c

d

e

Shift (δ, ppm) Peak Pattern Integration Assignment

4.10 Triplet 2 OCH2 d-H’s 2.05 singlet 3 CH3CO e-H’s 1.60 multiplet 2 OCH2CH2 c-H’s 1.45 multiplet 2 CH2CH3 b-H’s 0.93 triplet 3 CH2CH3 a-H’s

Note: The integrations are integers and correspond to the # of H’s in the true structure, not the integrations from NUTS. The integrations from NUTS may be 3.3 or 2.15,

etc…and you cannot have 3.3 H’s. The shifts are reported downfield to upfield (largest δ to smallest δ). Assignments are done by bolding the appropriate H’s and with a lettering system

as shown above.

3. In your Discussion section, include a section discussing the data obtained from the NMR and its relevance to the experiment.

4. In experiments involving identification of unknown compounds, a thorough discussion of how the structure of the compound was determined from the NMR needs to be included, discussing chemical shift, integrations, splitting and coupling.

5. In reaction-based experiments where the structure of the product is known, there should be a discussion of how the NMR data supports that the desired product

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was formed not only from indicative peaks found in the product, but also the absence of peaks that would be found in the starting materials or side products. For example, for the formation of the ester n-butyl acetate from n-butyl alcohol and acetic acid:

The CH2 shift of (d) for the product is higher the same shift would be for n-butyl alcohol, because the electron-withdrawing acetyl group deshields these protons. This indicates that the ester has formed. Also, the spectrum does not show any broad singlets that integrate to 1H in either the 2-3 ppm range (which would indicate an alcohol), or the 10-12 ppm range (which would indicate a carboxylic acid). Taken together, this evidence indicates that indeed the ester was formed.

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Experiment #1: Isolation of the Components of BC Powder OVERVIEW: BC Powder, an over the counter pain reliever, contains three components: acetylsalicylic acid (aspirin), caffeine, and salicylamide:

Each component contains certain functional groups that cause them to be either an acidic, basic or neutral compound. Most organic compounds, like benzoic acid, are not very soluble in aqueous solutions. However, if the compound is converted to a salt, like sodium benzoate, then they become water-soluble:

Benzoic acid is an acidic compound, so the reaction with a base (NaOH) causes the formation of the conjugate base (benzoate anion). Addition of an acid (HCl) converts the conjugate base back to the acid. When a mixture of compounds is dissolved in one liquid (for example, ethyl acetate) and another immiscible liquid is added (like an aqueous sodium hydroxide solution), the components will be partitioned, or distributed, between the two solutions based upon their solubility in each. In this case, the benzoic acid would be converted it to its water-soluble salt and reside mainly in the aqueous solution. Basic and neutral compounds would not react with the base and would therefore remain in the organic solution. This way, the components can be separated. This technique is called extraction, and is a very useful way to isolate components from mixtures. It is sometimes used to isolate useful components from natural products. Using the technique of extraction, you will separate the components and by partitioning them between an organic solution and aqueous solutions of various pH values. Another technique that will be used is recrystallization. Recrystallization is a purification technique that is used to separate impurities from a compound based upon differences in solubility. You will use recrystallization to purify one of the three components and compare its purity to when it was first isolated by extraction. There are four parts to the experiment, which will be completed over two weeks.

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CHALLENGE: Your challenge in this experiment is to isolate the components of BC powder by extraction, identify each component and determine the purity by melting point and TLC analysis; then recrystallize the recovered aspirin and compare its purity to when it was isolated by extraction. TECHNIQUES AND CONCEPTS: You will learn the technique of liquid extraction for the separation of acidic, basic, and neutral organic compounds on the basis of their solubility in immiscible phases, as well as the utilization of thin-layer chromatography (TLC), melting point analysis in determining the purity of a compound, and recrystallization as a purification technique. The concept of acid-base chemistry with respect to organic functional groups is introduced. READ: Operational Organic Chemistry, pp.585-587 (Cleaning and Drying Glassware, Using Specialized Glassware), 592-601 (Weighing, Measuring Volume, Making Transfers), 626-629 (Gravity Filtration), 635-645 (Extraction), 665-673 (Thin-Layer Chromatography), 680-681 (Drying Liquids), 692-704 (Recrystallization), 737-744 (Melting Point), 834-836 (Laboratory Equipment), 843-847 (Calculations for Organic Synthesis) PRELAB: In your lab notebook, write the following information before coming to lab: ü Summarized procedure (fill in on left side of page only, leaving right side for

observations and procedural changes made during lab period); ü Calculate the expected mass of each component for 2 packages of BC powder; ü Literature values for melting point of each component; ü Flow chart outlining the experiment, indicating which components were in the

organic and aqueous layers at each point; indicate solutions next to the arrows (see Operational Organic Chemistry p. 847-848 on how to make a flow diagram and p. 51 for example)

PROCEDURE: Part 1: Extraction • Accurately weigh the contents of 2 envelopes of BC powder into a tared 100-mL

beaker (See How to Tare a Flask page 49). Add 20 mL ethyl acetate and 10 mL saturated NaHCO3 solution. Swirl until all of the solids have dissolved (may take a few minutes). Set up a 125-mL separatory funnel. Make sure the stopcock is closed and pour in the solution from the beaker. Set out three beakers to collect the extracts.

• Insert a stopper in the top of the funnel. (See How to Use a Separatory Funnel page 46). Make sure that the stopper is completely inserted. Keep two fingers over the stopper as you shake to prevent the stopper from falling out. Be sure to point funnel away from other people and yourself.

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• Invert the funnel and gently shake. Carefully vent by opening the stopcock while the funnel is inverted to release pressure. Drain aqueous layer into beaker and label it “NaHCO3 extract”.

• Add another 10 mL saturated NaHCO3 solution to the separatory funnel. Insert stopper and shake as before while carefully venting. Drain aqueous layer into “NaHCO3 extract” beaker with first NaHCO3 extract. Set aside.

• Add 10 mL 3M HCl to separatory funnel. Insert stopper and shake as before while carefully venting. Drain aqueous layer into beaker labeled “HCl extract”.

• Add another 10 mL 3M HCl to separatory funnel. Insert stopper and shake as before while carefully venting. Drain aqueous layer “HCl extract” beaker with first HCl extract.

• Drain organic layer into third beaker and label it “organic layer”. For each solution, follow the instructions below (See How to Perform a Gravity Filtration page 47, How to Use the Rotary Evaporator page 47 and How to Tare a Flask page 49): Organic Layer Workup:

o To remove any remaining water, add a scoop of anhydrous magnesium sulfate (enough to cover the end of the spatula) to the beaker labeled “organic layer” and swirl. If solution is cloudy, add another scoop (no more than 3-4 scoops max) and swirl until not cloudy, which indicates residual water has been absorbed by magnesium sulfate.

o Gravity filter the solution into a tared 100-mL round bottom flask. Place flask on rotary evaporator and remove ethyl acetate. Weigh flask to obtain weight of solid. Remove solid from flask and place in a labeled vial.

NaHCO3 Extract Workup: o Obtain a 2-inch strip of pH paper. Place beaker labeled “NaHCO3 extract” in

an ice water bath. With swirling, slowly add 6M HCl and check pH periodically until pH reaches 6, then add an extra 10 mL of 6M HCl to ensure complete neutralization. A white precipitate should form.

o Stir the solution for several minutes to ensure complete neutralization. Set up a vacuum filtration flask, topped with a Büchner funnel.

o Attach the hose from the vacuum trap in the hood (do NOT connect directly to the aspirator!)

o Obtain a circular piece of filter paper and place in the funnel. Wet the paper with a small amount of cold water, then turn on the aspirator.

o Vacuum filter the solid, washing with cold water to remove any residual traces of HCl. Allow the solid to dry over vacuum. Once it is dry, transfer solid to a tared labeled vial.

HCl Extract Workup: o Obtain a 2-inch strip of pH paper. Place beaker labeled “HCl extract” into ice

bath. With swirling, slowly add 6M NaOH and check pH periodically until pH reaches 8, then add an extra 10 mL of 6M NaOH to ensure complete neutralization.

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o Add 10 mL ethyl acetate to the beaker and swirl to dissolve any solids. Place solution into separatory funnel. Shake funnel and vent. Drain aqueous layer back into “HCl extract” beaker. Drain organic layer into a separate clean Erlenmeyer flask.

o Place the aqueous solution back into the separatory funnel. Add another 10 mL ethyl acetate. Shake funnel and vent. Drain aqueous layer back into “HCl extract” beaker. Drain organic layer into Erlenmeyer flask with organic layer from previous step.

o To remove water, add a scoop of magnesium sulfate to the organic layer and swirl. If solution is cloudy, add another scoop and swirl until not cloudy (3-4 scoops).

o Gravity filter the solution into a tared 100-mL round bottom flask. Place flask on rotary evaporator and remove solvent. Weigh flask to obtain weight of solid. Remove solid from flask and place in a labeled vial.

Part 2: TLC Analysis (NOTE: See How To Perform TLC Analysis page 49 ) • Set up six vials. In the first three, place a small amount of each standard compound

and mark the vials “A” (acetylsalicylic acid), “C” (caffeine), and “S” (salicylamide). In the last three vials, place a small amount of solid from each extraction step and mark the vials “OL” (organic layer), “AE” (HCl extract), and “BE” (NaHCO3 extract). Add about 5 drops of acetone to each vial and swirl to dissolve.

• Obtain 5 mL of acetone and 5 mL of hexane and mix them together. This will be your developing solvent (50:50 acetone/hexane). Set up a 100-mL beaker with a half-circle of filter paper fitted to the inside of the beaker. Rinse the beaker out with 1-2 mL of the developing solvent, wetting the filter paper. Add enough solvent to the beaker to just cover the bottom. Cover the top with a watch glass.

• Obtain 2 TLC plates and one spotter. On each TLC plate, lightly draw a horizontal line with a pencil (no pens!) about 1-2 cm from the bottom of the plate. Make 6 marks (thin vertical lines) evenly spaced along the line. Label each spot underneath with a pencil (A, C, or S) for the first three marks and (OL, AE, or BE) for the next three. On the first three marks, carefully spot one of each of the standard compounds (A, C, or S); then spots one of the extracted compounds (OL, AE, or BE) on the next three marks. Don’t overload the spots; a small spot works best. [You might prepare two plates, one with light spots and one with heavier spots, to get a feel for the best amount of material to spot on a TLC plate.] Note: the circles below represent the sizes of the spots, NOT the markings you should make with the pencil.

• Place the TLC plate into the beaker and cover with the watch glass. Allow the solvent

to climb within 1-2 cm of the top of the plate. Take the plate out of the beaker and

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draw a line where the solvent stopped. Using a UV lamp, circle the spots on the plate lightly with a pencil. Compare the spots for each of your extracts to the standard compounds. Calculate the Rf value for each of the three components (acetylsalicylic acid, caffeine, and salicylamide) and record the values in your lab notebook.

Part 3: Melting Point Range Analysis • Let the all of the solids dry completely before attempting melting point analysis. • Load a small amount of each solid into separate melting point capillary tubes (see

How to Obtain a Melting Point Range page 49). You should prepare two tubes of each solid, one for a “fast run”, and another for a “slow run”.

• Obtain the melting point ranges for the three solids and record the results in your notebook. The starting point of the range is when the sample begins to liquefy and the final point of the range is when the sample has completely liquefied. Be sure to note the time it takes for the sample to melt.

Part 4: Recrystallization • Place 1 gram of the isolated aspirin (or all if it if not enough was recovered) into a 50

mL Erlenmeyer flask with a boiling stick. • Put ~20 mL of toluene into another 50 mL Erlenmeyer flask with a boiling stick, and

bring the toluene to a boil. • Carefully add the boiling toluene to the aspirin until just enough has been added to

fully dissolve the aspirin. If there is insoluble material, then heat the flask containing the aspirin and toluene to a boil until all material dissolves. If not, then just remove the boiling stick from the solution and set the Erlenmeyer on a cork ring in the hood.

• Once the solution has cooled to room temperature, place in an ice bath for 10-15 minutes. If crystals have not formed, either dip a stir rod into the solution and allow the solvent to evaporate off before dipping it in the solution again, or scratch the bottom of the flask carefully with a glass stir rod. If crystals still do not form, ask a TA for assistance.

• Collect the crystals by vacuum filtration and measure the mass and melting point of the recrystallized product.

LAB REPORT: Follow the Lab Report Guidelines included with this syllabus. Report should include: ü Balanced equations for reactions involved during extraction and neutralization ü Flow diagram for the extraction procedure, indicating which components were in the

organic and aqueous layers at each point; indicate solutions next to the arrows ü Summary table for data including percent recovery and melting point ranges for all

three extracted components ü Calculate percent recovery (experimental mass/theoretical mass * 100%) for each

component. Include in summary table and show calculations. ü Include drawings of TLC plates, tabulate Rf values for all three components ü For the discussion portion: ü Discuss what the results of the extraction indicate about each component; for each

extraction, is the aqueous solution: strongly acidic, strongly basic or weakly basic? What does that indicate about the compound that dissolves in that solution?

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ü Discuss the percent recovery for each component and how it could have been affected (i.e. spillage, insufficient neutralization, etc.)

ü Discuss your results from melting point and TLC analysis and what they indicate about the purity of each component

ü Discuss the results of comparing the melting point of recrystallized aspirin to the melting point of the aspirin after isolating it from extraction, and compare recrystallization and extraction as purification techniques.

QUESTIONS: A handout will be given to you containing the postlab questions for this experiment. Use complete sentences to answer the questions. Any structures and mechanisms should be drawn with appropriate software, not hand-drawn. The assigned readings are usually an excellent place to being searching for answers.

Make sure that your answers to the postlab questions are included at the end of your postlab report.

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Experiment #2: Preparation of Synthetic Banana Oil OVERVIEW: Many of the flavors and perfumes we use today are derived from compounds found in nature. Usually, these compounds are separated from natural sources by a variety of techniques, like extraction or distillation. Sometimes, however, there may be only a limited supply of the natural source, or the process required to isolate a certain component is simply too difficult or expensive to be commercially viable. In these cases, scientists will often find a method to cheaply and efficiently prepare the component synthetically. In this experiment you will prepare isoamyl acetate, which is commercially sold as synthetic banana oil. Isoamyl acetate is synthesized by heating isoamyl alcohol, glacial acetic acid, and sulfuric acid (catalyst) in hexane, followed by fractional distillation to acquire the desired product. The esterification is a reversible reaction and exists in equilibrium, as illustrated below:

Removing one of the components during the reaction can shift the equilibrium position. In this case, by removing water from the reaction mixture, the equilibrium will be shifted to the right, and more of the products will be formed. This will increase the efficiency of the reaction. One method to remove water from a reaction mixture is azeotropic distillation. When two liquids form an azeotrope, the boiling point of the mixture is related to the relative concentration of the components. There are two types of azeotropes: maximum-boiling and minimum-boiling azeotropes. In this experiment, hexane forms a minimum-boiling azeotrope with water. A Dean-Stark trap allows for the separation of water from the refluxing mixture. As the vapor (containing a mixture of water and hexane) condenses, the denser water becomes trapped in the sidearm while the lighter hexane flows back into the reaction flask. This way the water is continuously removed from the reaction. CHALLENGE: Your challenge in this experiment is to synthesize isoamyl acetate and purify it by fractional distillation. You will also characterize the product by IR spectroscopy and assess its purity by gas chromatography. TECHNIQUES AND CONCEPTS: You will learn the technique of gas chromatography as a method of qualitative and quantitative analysis, as well as the technique of NMR spectroscopy to characterize a compound and assess the product’s purity. Concepts introduced include esterification, azeotropes, LeChatelier’s principle and driven equilibrium.

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READ: Operational Organic Chemistry, pp.70-77 (Preparation of Synthetic Banana Oil; note procedural changes!), 621-622 (Water Separation), 758-769 (Gas Chromatography), 802-815 (Nuclear Magnetic Resonance Spectroscopy) Also review: pp. 606-608 (Hot Plates and Heating Blocks), 609 (Smooth Boiling Devices), 678-682 (Washing Liquids and Drying Liquids), 710-719 (Simple Distillation), 727-736 (Fractional Distillation) 744-746 (Boiling Point), 773-792 (Infrared Spectroscopy; also refer to pp.793-801 for Characteristic Infrared Bands) PRELAB: In your lab notebook, write the following information before coming to lab: ü Balanced equation for esterification reaction; ü Mechanism for the esterification (separate from balanced equation); ü Table of reagents containing all starting materials and products, with data filled in for

all pertinent physical properties (MW, bp/mp, density, concentration, etc.); ü Density and boiling point of solvents (hexane) ü Theoretical yield for products (water too!); ü Summarized procedure (fill in on left side of page only, leaving right side for

observations and procedure changes made during lab); ü Calculate the volume of water that will be formed during the reaction (you will use

this to monitor the progress of the reaction). PROCEDURE: • Into a 50-mL round bottom flask, place 7.5 mL of isoamyl alcohol, 4.0 mL of glacial

acetic acid (17.4M), 1 mL of concentrated sulfuric acid, and 7 mL hexane along with 2 or 3 boiling chips. (To get an accurate mass of isoamyl alcohol it is recommended to weigh the vial and sample before, and once added clean the vial, allow to dry and get weigh again. The difference is the starting material mass).

• Obtain a Dean-Stark trap (See How to Set Up a Dean-Stark Trap page 51). Refer to your prelab and find the volume of water that should be generated during the reaction. In a graduated cylinder, measure out hexane to that volume. Add the hexane from the graduated cylinder into the Dean-Stark trap. Use a marker to mark where the top of the solvent line is. This mark will help you determine when to stop the reaction. Fill the trap to the joint with hexane.

• Connect the trap with the flask and condenser. Make sure water is flowing through the condenser before you begin. Heat using a hot plate aluminum block until the mixture begins to reflux vigorously (hot plate setting should be close to maximum in the beginning until refluxing becomes vigorous, then heat should be slowly turned down to get a steady, vigorous reflux). DO NOT allow vapor to escape the top of the condenser! Wrap the tube in between the flask and the condenser, and the top of the flask in aluminum foil to ensure that heat is contained within those areas. Reflux until the water level in the trap reaches the mark you made (0.5 to 1.5 hours). Discontinue heating and allow reaction flask to cool completely to room temperature.

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• Transfer contents of the reaction flask and trap into a 125-mL separatory funnel. Remove the aqueous layer. Wash the organic layer twice with 10 mL portions of water and set the aqueous washes aside.

• Add ~10 mL of 5% NaHCO3 solution to the organic layer in the separatory funnel. Continuously swirl the contents with the top of the funnel open until fizzing decreases. Stopper the funnel and gently shake, venting often to release any pressure generated by CO2 gas. Remove the aqueous layer and set aside.

• Wash the organic layer with ~10 mL brine (saturated NaCl solution). Allow the two layers to set in the funnel for several minutes before separating. The organic layer should become not cloudy.

• Transfer the organic layer to a clean dry flask and add anhydrous magnesium sulfate with swirling until solution is no longer cloudy. Gravity filter the organic layer into a clean, dry 25-mL round bottom flask equipped with 2-3 boiling chips. Tightly stopper the flask and wrap stopper in parafilm. Return Dean-Stark trap before leaving lab!

• Set up a fractional distillation apparatus, with the flask containing your crude product

as the stillpot. Make sure you place the thermometer correctly. Collect fractions as indicated by temperature changes at the top of the column. The fraction distilling above 135°C should be nearly pure isoamyl acetate. You may have to wrap the apparatus in aluminum foil to maintain higher temperatures.

• Collect the final fraction in a tared round bottom flask. Record the boiling point range for the product and determine the weight and yield.

• Save a small sample for IR analysis and prepare an NMR sample of the product and submit it for analysis. NOTE: Once you have been notified that your NMR has been run, you are responsible for downloading the FID file as soon as possible and checking that there are no issues with the file. You must inform a TA immediately if there is an issue so the TA can help to resolve it in a timely manner. If you wait until the day before the report is due and a problem occurs, the TAs will not be able to help you and you will still have to turn in your lab report on time.

LAB REPORT: Follow the Lab Report Guidelines included with this syllabus. Report should include: ü Balanced equation for esterification reaction ü Mechanism of esterification reaction (It is advisable to look up esterification in your

Chemistry 236 text) ü Calculate percent yield (experimental yield/theoretical yield * 100%) ü Summary table with experimental yield, percent yield and boiling point range for

product ü Summary table for IR spectrum data (include original printout with report) ü Summary table for GC chromatogram data (include original printout with report) ü For the discussion portion: ü Discuss LeChatelier’s principle and why a Dean-Stark trap is used ü Discuss percent yield of product and and how it could have been affected (i.e.

reaction time, insufficient distillation, etc.)

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ü Fully interpret the data on the IR spectrum. ü Discuss the purity of your product based on bp, IR, and GC analysis QUESTIONS: A handout will be given to you containing the postlab questions for this experiment. Use complete sentences to answer the questions. Any structures and mechanisms should be drawn with appropriate software, not hand-drawn. The assigned readings are usually an excellent place to being searching for answers. Make sure that your answers to the postlab questions are included at the end of your postlab report.

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Experiment #3: Identification of a Conjugated Diene in Eucalyptus Oil OVERVIEW: Eucalyptus oil is a common homeopathic remedy that is often used in respiratory illnesses. The most widely used variety is extracted from the species Eucalyptus globulus, and is composed mainly of eucalyptol:

Eucalyptol may cause inflammatory reactions in some people, however. Another species of eucalyptus, Eucalyptus dives, which does not contain eucalyptol, has been indicated to be a more hypoallergenic option and can be used in topical applications. One of its components is believed to have other potential pharmaceutical applications, such as in the treatment of colds, malaria and fevers. It is thought to be one of the conjugated dienes below:

The isolation of natural products is a very important way to discover new drugs with interesting pharmaceutical properties. Researchers use a variety of methods to isolate components from natural sources, such as extraction or distillation. These methods are not efficient, however, when many of the components in the mixture have very similar properties. Another method to separate components is to form a derivative of the desired component by selectively reacting it with a specific reagent. The resulting product will then have different properties that will allow for separation of the product from the reaction mixture. In this experiment, you will isolate and identify the conjugated diene in the oil by forming a derivative of the component so that it will form a solid and precipitate from the solution. You will use the Diels-Alder reaction, in which a conjugated diene reacts with a dienophile (in this case maleic anhydride):

The Diels-Alder reaction is a highly efficient method to form carbon-carbon bonds. Since the product contains all of the atoms from the starting materials, the reaction is considered to have 100% atom economy. Atom economy has become highly desirable in green chemistry, to reduce the amount of waste produced during industrial processes. The Diels-Alder reaction is also stereoselective, as usually only one stereoisomer is likely to form out of several different possible stereoisomers (see textbook for more in-depth explanation).

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In order to determine how much of the reagent is needed, you will use GC analysis to calculate the fraction of the active component in the oil based upon the area of the peaks. The TA will provide you with a correction factor based upon a standard calibration of the instrument. Once the solid has been isolated, you will purify the compound by recrystallization and determine the identity of the derivative by obtaining its melting point range and interpreting the NMR spectrum. CHALLENGE: Your challenge in this experiment is to isolate and identify a component in Eucalyptus dives oil by performing a Diels-Alder reaction to form a solid and purify it by recrystallization. TECHNIQUES AND CONCEPTS: This experiment illustrates the concept of changing a physical property by formation of a derivative to isolate a component from a mixture. Utilization of a melting point and NMR spectroscopy to identify an unknown compound is also illustrated. READ: Operational Organic Chemistry, pp. 271-277 (Identification of a Conjugated Diene from Eucalyptus Oil; note procedural changes!) Also: Review Basic Operations from previous experiments; (Gas Chromatography), 773-792 (Infrared Spectroscopy; also refer to pp.793-801 for Characteristic Infrared Bands), 609-613 (Heating Under Reflux), 629-633 (Vacuum Filtration), 685-687 (Washing and Drying Solids), 692-700 (Recrystallization), 802-811 (NMR Spectroscopy) PRELAB: In your lab notebook, write the following information before coming to lab: ü Balanced equation for the Diels-Alder reaction (use molecular formula for product); ü Structures of all potential products with β-myrcene, allo-ocimene, α-phellandrene,

andα-terpinene; ü Table of reagents containing starting materials (include all potential dienes from

above) and potential products (there are 5), with the data for all pertinent physical properties (MW, bp/mp, density, concentration, etc.). Data other than MW and MP are not necessary for potential products. You may refer to the products as “β-myrcene adduct, allo-ocimene adduct, etc.;

ü Summarized procedure (fill in on left side of page only, leaving right side for observations and procedural changes made during lab period).

PROCEDURE: ***NOTE: All glassware must be dry for the reflux portion of this experiment*** • You will receive a GC chromatogram of the Eucalyptus dives oil (via compass).

Examine the chromatogram and determine the relative concentration of the peak corresponding to the diene (the percent area is roughly equivalent to the percent mass). Then calculate the amount of maleic anhydride needed for the reaction.

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• In a 25-mL round-bottom flask, dissolve 5.0 grams of Eucalyptus dives oil in 10 mL of petroleum ether. Add calculated amount of maleic anhydride and top the flask with a reflux condenser. Be sure water is flowing in your condenser before you begin heating. Reflux the reaction mixture for approximately 45-60 minutes.

• Transfer the warm reaction mixture to a small beaker. Cover with a watch glass and let it cool slowly to room temperature. If no crystals form after cooling completely, dip a stirring rod in the solution and pull it out. Let the ether evaporate from the rod and reinsert it in the solution. If that doesn’t work, scratch the side of the flask with the tip of the rod. If neither method works, ask the TA.

• Once crystallization seems complete, cool the flask in an ice-water bath for 5 minutes. Collect the crystals by vacuum filtration. Wash the crystals with 10 mL of cold petroleum ether.

• Weigh the crude product before performing mixed-solvent recrystallization using acetone and water to purify it. Dissolve the crude product in minimal acetone. Add water to the solution. You should see crystals form immediately. Continue to add water until no new crystallization is observed. Vacuum filter the crystals, wash with cold water, and dry with suction. Then weigh the pure product, measure its melting point, and acquire and IR spectrum.

LAB REPORT: Follow the Lab Report Guidelines included with this syllabus. Report should include: ü Balanced equation for the Diels-Alder reaction (show stereochemistry of product) ü Mechanism of the Diels-Alder reaction (this is separate from the balanced equation!) ü Calculate percent yield (experimental yield/theoretical yield * 100%) ü Summary table with experimental yield, percent yield and mp for product ü Summary table for IR spectrum data (include original printout with report) ü Summary table for GC chromatogram data (include original printout with report) ü Calculate the relative amount of starting diene based on experimental yield of product

and compare this to the relative amount of starting diene as determined by GC analysis

ü For the discussion portion: ü Discuss how you decided upon the identity of the diene ü Discuss percent yield of product and and how it could have been affected by reaction

conditions (i.e. reaction time, temperature of reflux, etc.) ü Discuss the purity of your product based on mp and IR QUESTIONS: A handout will be given to you containing the postlab questions for this experiment. Use complete sentences to answer the questions. Any structures and mechanisms should be drawn with appropriate software, not hand-drawn. The assigned readings are usually an excellent place to being searching for answers. Make sure that your answers to the postlab questions are included at the end of your postlab report.

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Experiment #4: NMR exercises

Pre-lab and lab exercises are on compass.

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Experiment #5: Acetylation of Ferrocene OVERVIEW: Benzene, which is a common component of petroleum, is often converted to other useful compounds by various methods of functionalization. One method often performed at industrial scale is the Friedel-Crafts acylation, which adds a ketone functionality to the ring. These ketones can then be further convertered into other useful compounds. The Friedel-Crafts acylation of benzene is a type of electrophilic aromatic substitution reaction. The major drawback is that it usually requires aluminium chloride, which is toxic, as the catalyst. Problems such as this have driven many industries to search for cleaner, greener methods. Some compounds are more susceptible to electrophilic aromatic substitution reactions and can be acetylated under milder, less toxic conditions. Ferrocene, Fe(C5H5)2, is an organometallic compound with an Fe2+ cation coordinated between two C5H5

- anions:

Ferrocene has properties similar to benzene in that the cyclopentadiene anion rings have six delocalized pi electrons. Ferrocene, however, can be acetylated under milder conditions with phosphoric acid as the catalyst. The Friedel-Crafts acylation of ferrocene is shown below:

The acylium ion, CH3CO+, is the electrophile that is generated from acetic anhydride. It reacts with ferrocene to yield either 1-acetylferrocene or 1,1'-diacetylferrocene. Since the acyl group is a deactivating group, the second substitution is less likely to occur and so very little of the disubstituted product is formed. In this experiment, you will perform the acetylation of ferrocene and separate the product from the reaction mixture by liquid column chromatography. Ferrocene and its derivatives are very brightly colored compounds, so you will easily be able to visually monitor the progress of the separation of the components on the column.

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CHALLENGE: Your challenge in this experiment is to perform the Friedel-Crafts acylation of ferrocene, isolate the desired product by liquid column chromatography, and identify the products by IR and NMR spectroscopy and melting points. TECHNIQUES AND CONCEPTS: The main technique introduced in this experiment is liquid column chromatography. TLC will be used to distinguish which bands on the column correspond to starting materials and products. Also illustrated is the concept of Friedel-Crafts acylation. READ: Operational Organic Chemistry, pp. 306-308 (Friedel-Crafts reaction theory), 609-613 (Heating Under Reflux),656-664 (Liquid-Solid Column Chromatography) Also: Review Basic Operations from previous experiments, specifically 629-633 (Vacuum Filtration), 665-673 (Thin-Layer Chromatography), 737-744 (Melting Point) 773-792 (Infrared Spectroscopy; also refer to pp.793-801 for Characteristic Infrared Bands) PRELAB: In your lab notebook, write the following information before coming to lab: ü Balanced equation for the Friedel-Crafts acylation; ü Mechanism for the Freidel-Crafts acylation (separate from equation); ü Theoretical yield for all potential products; ü Table of reagents containing all starting materials and possible products, with the data

for all pertinent physical properties (MW, bp/mp, density, etc.); ü Summarized procedure (fill in on left side of page only, leaving right side for

observations and procedural changes made during lab period). PROCEDURE: Part 1: Synthesis and TLC analysis • Accurately weigh 0.5 g of ferrocene and transfer to a dry 25-mL round bottom flask.

Add 5.0 mL of acetic anhydride and swirl. Then slowly add 1.0 mL of 85% phosphoric acid and swirl the mixture.

• Attach a reflux condenser (see How to Perform a Reflux page 56) and heat the reaction to reflux on the aluminum blocks for 1 hour (start timing from when the solvent condenses on the reflux condenser). After 1 hour, remove the heat source and allow solution to cool to room temperature (about 10 minutes).

• Pour the solution onto approximately 40 g of ice in a large beaker. Neutralize the solution by dropwise addition of 6M NaOH, checking the pH periodically until the solution is neutral, then add an extra 10 mL of 6M NaOH.

• Cool the solution in an ice-water bath and collect the crude product by vacuum filtration. Remove as much water as possible by allowing the solid to remain under vacuum filtration for another 15 minutes. Obtain the weight of the crude product.

• While the solid is drying, prepare a TLC plate with two lanes. Dissolve a small amount of ferrocene in toluene (1-2 drops) and spot the first lane. Dissolve a small amount of the crude solid in a few drops of toluene and spot in the second lane.

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• Mix 5 mL of hexane and 5 mL of ethyl acetate (1:1 hexane/ethyl acetate) for eluent. Prepare TLC chamber and develop TLC plate. Record results in your notebook, including a sketch of TLC plate.

Part 2: Column chromatography and TLC analysis • Obtain a chromatography column and securely clamp it in a vertical position (see

How to Set Up a Chromatography Column page 58). Pack a small amount of cotton into the tip of the column and add a small layer of sand over the cotton to provide a level surface for the stationary phase.

• Prepare first eluent by mixing 90 mL of hexane and 10 mL of ethyl acetate (9:1 hexane/ethyl acetate). Close the stopcock and add several mL of eluent to the column. Drain a small amount of eluent from the column then close the stopcock, leaving a small layer of liquid in the bottom of the column.

• To prepare the stationary phase, obtain about 18 g of silica in a small beaker. With stirring, add enough of the 9:1 hexane/ethyl acetate eluent to cover the silica. Stir until the silica forms a slurry (add more eluent if necessary). Pour the slurry into the column in a steady stream (silica settles quickly, so slurry must be poured as quickly as possible). Open the stopcock and allow the solvent to drain to just above the top of the silica.

• While draining, tap the side of the column continuously with a piece of tubing so that the silica settles evenly and uniformly. Once the solvent has reached just above the silica, close the stopcock.

• Add a small layer of sand to the top of the column. Drain the eluent until the level is just below the sand, but not below the top of the silica.

• Dissolve the crude product in a minimal amount of toluene (no more than 1.5 mL; there may be some insoluble residue, just ignore this). Pipette the toluene solution on top of the sand layer. Rinse the container with another 1 mL of toluene and add this to the column. Drain the solvent level until it is again just below the sand layer, but above the silica layer.

• Carefully fill the column with 9:1 hexane/ethyl acetate eluent without disturbing the sand layer. Open the stopcock and collect the solvent in a test tube to a level that you decide. Continue collecting the portions in test tubes to approximately this level. A bright yellow band will move down the column. As the solvent level becomes low in the column, add more eluent until the yellow band is completely off the column and the first orange band is either off the column or near the bottom of the stationary phase.

• In order to elute the next bands, the eluent system must be changed. For the second eluent, combine 50 mL of hexane and 50 mL ethyl acetate (1:1 hexane/ethyl acetate). Allow the solvent to drain to just below the sand layer and close the stopcock. Carefully add the 1:1 hexane/ethyl acetate eluent and re-open the stopcock.

• Continue collecting the portions in test tubes, adding solvent to the column as needed. Perform TLC analysis on each portion to determine what compounds are in each portion. Place the solutions for each pure compound (one spot in each lane) in a tared round bottom flask and remove the solvent. Let the solids dry until next week.

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• Obtain the mass and melting point rangefor each component obtained from the column purification. Using the melting point, determine which band corresponds to 1-acetylferrocene, acquire an IR spectrum, and submit a sample for NMR. Submit the product(s) in labeled vials.

LAB REPORT: Follow the Lab Report Guidelines included with this syllabus. Report should include: ü Balanced equation for formation of acetylferrocene and diacetylferrocene ü Mechanism of Friedel-Crafts acylation – only mechanism for formation of

acetylferrocene is necessary, not diacetylferrocene. ü Calculate percent yield (experimental yield/theoretical yield * 100%) for all products ü Summary table with experimental yield, percent yield and mp for all products ü Summary table for IR and NMR spectral data (include original printouts with report) ü Fully interpret the data on the IR and NMR spectra; compare the spectra of the

products to the spectra of ferrocene, point out and explain any significant similarities or differences

ü Include a drawing of your TLC plates, labeling the spots and calculate the Rf values ü Explain in detail how you determined the which band corresponded to which

component ü Discuss the effectiveness of your reaction based on the yield. ü Based on spectral analysis and mp, comment on the purity of your products QUESTIONS: A handout will be given to you containing the postlab questions for this experiment. Use complete sentences to answer the questions. Any structures and mechanisms should be drawn with appropriate software, not hand-drawn. The assigned readings are usually an excellent place to being searching for answers. Make sure that your answers to the postlab questions are included at the end of your postlab report.

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Experiment #6: An Unexpected Reaction of 2,3-dimethyl-2,3-butanediol OVERVIEW: You are working as a synthetic chemist for a company and have been asked to investigate an efficient method to produce the compound 2,3-dimethyl-1,3-butadiene. You decide to do the classic acid-catalyzed dehydration of 2,3-dimethyl-2,3-butanediol to obtain the conjugated diene. You know that the diene has a boiling point of about 70˚C. To your surprise and disappointment, you obtain a liquid with the molecular formula C6H12O:

HO OHH2SO4

C6H12O 2H2O

Researchers often encounter the problem of reactions not proceeding as they should, even when using methods that are usually straightforward. In order to determine whether a reaction has proceeded as desired, the product has to be qualitatively analyzed. There are a variety of methods used to obtain the structural information of a compound. You will utilize one of these methods, infrared (IR) spectroscopy. You will perform the acid-catalyzed reaction with 2,3-dimethyl-2,3-butanediol and determine the identity of the unexpected product by IR and boiling point. You will purify the product by fractional distillation. CHALLENGE: Your challenge in this experiment is to determine what is actually happening during the reaction by isolating the unknown product and determining its structure by IR and boiling point. TECHNIQUES AND CONCEPTS: You will learn the technique IR analysis as a method to determine the structure of an unknown compound. You will also utilize the technique of distillation for the purification of liquids. READ: Operational Organic Chemistry, pp. 265-270 (An Unexpected Reaction of 2,3-Dimethyl-2,3-butanediol; note procedural changes!), 606-608 (Hot Plates and Heating Blocks), 609 (Smooth Boiling Devices), 678-682 (Washing Liquids and Drying Liquids),710-719 (Simple Distillation), 727-736 (Fractional Distillation), 773-792 (Infrared Spectroscopy; also refer to pp.793-801 for Characteristic Infrared Bands) PRELAB: In your lab notebook, write the following information before coming to lab: ü Balanced equation for the reaction (use molecular formula for product); ü Theoretical yield for the potential product; ü Table of reagents containing all starting materials and potential products, with the

data for all pertinent physical properties (MW, bp/mp, density, etc.); ü Summarized procedure (fill in on left side of page only, leaving right side for

observations and procedure changes made during lab).

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PROCEDURE: (You must monitor/record your boiling points carefully!) • Weigh out 3.6 grams of 2,3-dimethyl-2,3-butanediol (2,3-dimethyl-2,3-butanediol)

and transfer to a 25-mL round bottom flask. Add 10 mL of 3M sulfuric acid and a magnetic stir bar to the flask.

• Set up a simple distillation apparatus (see How to Set Up a Simple Distillation page 57) with a 25-mL round bottom flask as the receiving flask. Be sure to place the receiving flask in an ice-water bath. Using a heating block, heat the solution until you have filled the receiving flask about half full (temperature should be over 100°C).

• Transfer the distillate to a separatory funnel. Rinse the round bottom flask with a few mL of distilled water and add this to the separatory funnel. Separate the organic layer from the aqueous layer.

• Place the organic layer back in the funnel. Add 6 mL of saturated sodium chloride to the funnel. Swirl the solution, then stopper the funnel and shake. Place the funnel back on the stand and remove the stopper. Let stand for several minutes. Separate the organic layer from the aqueous layer.

• Transfer the organic layer to a clean, dry Erlenmeyer flask. Add magnesium sulfate with swirling to dry the solution (until no longer cloudy). Filter the solution into a clean, dry round bottom flask.

• Purify the product by fractional distillation (use clean, dry glassware! See How to Set Up a Fractional Distillation page 54). In order to do this efficiently, add 2 mL DMF to the flask containing the product to be purified. There could possibly be two fractions: 70-75°C and the unknown. Be sure to record the boiling point range of each fraction. Collect the fractions in preweighed, clean, dry flasks (not a vial! Product is very volatile).

• Obtain an IR for each fraction that is obtained (see How to Obtain an IR Spectrum page 54).

LAB REPORT: Follow the Lab Report Guidelines included with this syllabus. Report should include: ü Balanced equation for formation of unexpected product ü Mechanism of formation of unexpected product ü Balanced equation for formation of diene ü Mechanism of formation of diene ü Calculate percent yield (experimental yield/theoretical yield * 100%) for all products ü Summary table with experimental yield, percent yield and bp for all products ü Summary table for IR spectral data (include original printouts with report) ü Fully interpret the data on the IR spectrum and explain in detail how you determined

the structure of the unexpected product ü Based on spectral analysis, comment on the purity of your product

QUESTIONS: A handout will be given to you containing the postlab questions for this experiment. Use complete sentences to answer the questions. Any structures and mechanisms should be drawn with appropriate software, not hand-drawn. The assigned readings are usually an excellent place to being searching for answers. Make sure that your answers to the postlab questions are included at the end of your postlab report.

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Experiment #7: Multi-step Synthesis of Fragrances OVERVIEW: Many commercially available fragrances contain benzyl ethers, such as methyl diantilis, which can be synthesized from 3-ethoxy-4-hydroxy benzaldehyde (ethyl vanillin) and methanol. Ethyl vanillin is a derivative of vanillin, which is the primary component of vanilla extract. The fragrance industry mainly uses ethyl vanillin because it produces a stronger “note”, or odor:

The presence of the phenol functionality on the ring gives the compound a warm “woody” scent, similar to the odor of vanilla. Many perfume makers have experimented with altering the position of the phenol, as well as substituting the phenol with other functional groups to see what effect these substitutions might have on the odor of the final product with odors ranging from “citrus” and “fruity” to “musky” and “amber”. In fact, there are many industries solely devoted to organoleptic chemistry, or the development of compounds that stimulate the olfactories and tantalize the taste buds. This is just one illustration of how the physical properties of a compound can be changed by modification of the structure. Chemists often synthesize a variety of compounds with slight changes in structure, called derivatives, to explore how changing certain functional groups affect the desired properties of each derivative. In this experiment, you will explore how the structure of the aldehyde and alcohol used to make benzyl ethers can affect the odor of the final product. You and your classmates will each synthesize a benzyl ether derivative. All students will use Aldehyde B and Alcohol 2. :

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You will perform a multi-step synthesis; a reduction followed by an etherification. You will isolate and characterize the intermediate as well as the final product.

CHALLENGE: Your challenge in this experiment is to carry out the multi-step synthesis of a benzyl ether derivative and compare its scent to your classmates’ derivatives to determine how the structure affects its odor. TECHNIQUES AND CONCEPTS: The primary objective of this experiment is to conduct a synthesis composed of multiple steps with characterization of the intermediates obtained. You will utilize the techniques you have learned up to this point to complete this task. You will also learn how to use TLC analysis as a method to monitor reaction progress. Concepts include reduction of a carbonyl group and formation of an ether from two alcohols. READ: Operational Organic Chemistry, pp. 246-252 (Borohydride Reduction of Vanillin to Vanillyl Alcohol; note procedural changes!) Also: Review Basic Operations from previous experiments, specifically 609-613 (Heating Under Reflux), 692-700 (Recrystallization), 665-673 (Thin-Layer Chromatography), 773-792 (Infrared Spectroscopy; also refer to pp.793-801 for Characteristic Infrared Bands), 802-815 (Nuclear Magnetic Resonance Spectrometry) PRELAB: In your lab notebook, write the following information before coming to lab: ü Balanced equations for the multi-step synthesis for your starting materials, drawing

the structure of your intermediate and final products; ü Mechanisms for reduction of your aldehyde and etherification with your alcohol

(separate from equations); ü Calculate amounts you will need for 10 millimoles (mmol) of your starting materials

for the first step, and 5 mmol of reagents (including the intermediate product) for the second step;

ü Theoretical yield for the intermediate and final products (based on 10 mmol and 5 mmol, respectively);

ü Table of reagents containing all starting materials and products, with the data for all pertinent physical properties (MW, bp/mp, density, etc.);

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PROCEDURE: Part 1: Reduction of aldehyde • In a 125-mL Erlenmeyer flask equipped with a magnetic stir-bar, dissolve 10 mmol of

the aldehyde in 10 mL of methanol. Cool the flask in an ice-water bath set on a magnetic stir plate. With stirring, add 0.4 grams sodium borohydride in small portions (approximately a spatula-tip full).

• Remove the flask from the ice-water bath and let the reaction mixture sit at room temperature until the bubbling has subsided (~20-30 minutes).

• Place the flask back in the ice-water bath and, with stirring, slowly add 10 mL of 3M HCl. Check that the pH is ≤4. If not add more HCl until solution is sufficiently acidic. Remove the flask from the ice-water bath and gently swirl until bubbling has subsided.

• Add 20 mL ethyl acetate to dissolve any solids and place the solution in a 125 mL separatory funnel. Drain the organic layer into a clean Erlenmeyer flask.

• Extract the organic layer two more times with 10 mL water then once with 10 mL saturated sodium chloride solution. Separate the layers and place the organic layer in a clean dry flask. Add magnesium sulfate to the organic layer with swirling until solution is not cloudy. Gravity filter the solution into a round bottom flask and evaporate the methylene chloride with the rotary evaporator.

• Obtain a mass on the resulting product and move on to the next step with no further purification.

Part 2: Etherification • Obtain the mass of your benzyl alcohol and calculate the yield. Be sure to save a

sample for IR and NMR analysis. After product is dry, weigh the flask to obtain the yield.

• Place 0.5 gram of Amberlyst® 15 beads into a 100 mL round bottom flask equipped with a magnetic stir bar. Wash the beads by adding 5 mL of the alcohol, swirling, then carefully pouring as much of the alcohol as possible out of the flask. Repeat the wash two more times.

• Add 5 mL alcohol to the beads and add a magnetic stir bar to the flask. Dissolve 5 mmol of the product from step 1 in 5 mL of the alcohol and add to the solution containing the beads.

• Remove one drop of the mixture and save for TLC analysis (see How to Perform TLC Analysis and section below). Attach a reflux condenser to the flask and reflux for 15 minutes with stirring by magnetic stir plate.

• Remove the flask from heat and let cool to room temperature. Remove one drop and perform TLC analysis (see below). If reaction is not complete, replace heat source and let reflux another 15 minutes. Let solution cool and remove another drop and perform TLC analysis. Repeat process until reaction appears to be complete by TLC analysis (that is, the starting benzyl alcohol no longer appears on the TLC plate).

• After reaction is complete, allow solution to cool to room temperature. Gravity filter the reaction mixture into a small beaker. Wash the round-bottom flask several times

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with a few mL of methylene chloride and pour them onto the filter paper to wash the beads thoroughly.

• Transfer the solution to a separatory funnel and add 20 mL of methylene chloride. Wash the organic solution three times with 10 mL distilled water.

• Place the organic layer in a clean dry Erlenmeyer flask. With swirling, add enough magnesium sulfate to dry the organic solution. Gravity filter the solution into a tared round bottom flask. Remove the methylene chloride via rotary evaporation.

• Obtain mass of your product before purification. TLC analysis: Dissolve each drop from the reaction mixture in 5 drops of acetone. Be sure to note at which time the drop was removed from the solution (before reflux, after 15 minutes, after 30 minutes, etc.) On the TLC plate, place each of the spots in order. The lane for the first drop is labeled as t=0, the next lane is labeled t=15, and so on. For the eluent, mix 5 mL of ethyl acetate and 5 mL of hexane (1:1 ethyl acetate/hexane). Run the TLC plate as you did in Experiment 1. To determine if the reaction is complete, examine the spots under UV lamp. The spots for the starting materials in lane t=0 should not be present in the later lanes. If there is still a significant amount of unreacted starting material present, continue refluxing and testing by TLC until the reaction is complete. You may need to add more acetone to the sample as it evaporates. Part 3: Column Chromatography • Judge from your previous TLC results in this experiment what a good solvent mixture

for column chromatography would be. • Perform column chromatography on the impure benzyl ether, keeping in mind all the

details about this technique you learned in Experiment 3. • Make sure you keep ALL the fractions until TLC has been preformed on them and

you have isolated your pure benzyl ether. • Obtain the mass, IR and NMR of your final pure product. LAB REPORT: Follow the Lab Report Guidelines included with this syllabus. Report should include: ü Balanced equation for the reduction of the aldehyde and subsequent acid-catalyzed

etherification ü Mechanism for aldehyde reduction ü Mechanism for acid-catalyzed etherification ü Calculate percent yield (experimental yield/theoretical yield * 100%) for all products ü Summary table with experimental yield, percent yield and mp where applicable for all

products ü Summary table for IR spectral data (include original printouts with report) ü Summary table for NMR spectral data (include original printouts with report) ü Fully interpret the data on both the IR and NMR spectra, including:

o Compare the IR spectrum of your intermediate product and final product, noting similarities and differences

o Compare the 1H-NMR spectrum of your intermediate product and final product, noting similarities and differences

o Comment on purity of your products ü Include a drawing of your TLC plate(s), labeling the spots and calculate the Rf values

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ü Explain in detail how you determined the etherification reaction was complete [The section below will not be completed this semester]

QUESTIONS: A handout will be given to you containing the postlab questions for this experiment. Use complete sentences to answer the questions. Any structures and mechanisms should be drawn with appropriate software, not hand-drawn. The assigned readings are usually an excellent place to being searching for answers. Make sure that your answers to the postlab questions are included at the end of your postlab report.

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Experiment #8: Enolate Chemistry – Chalcone Synthesis

OVERVIEW: Chalcones are molecular scaffolds of particular interest due to the variety of biological activities associated with them, including cytotoxic, antitumor, anti-inflammatory, antiplasmodial, immunosuppression, and antioxidant properties.1 They are intermediates in the biosynthesis of flavonoids, which also have many potential pharmaceutical uses. Chalcones are easily synthesized by the base-catalyzed aldol condensation of an aldehyde and a ketone:

CHALLENGE: Your challenge in this experiment is to design the synthesis, purification and characterization of a chalcone derivative, using the concepts and skills learned throughout the semester. TECHNIQUES AND CONCEPTS: The primary objective of this experiment is to utilize the techniques learned up to this point to synthesize, purify, and characterize a compound. The secondary objective is to learn to use TLC analysis to determine optimal conditions for purification by column chromatography. This experiment also illustrates carbonyl chemistry and aldol condensations. READ: Operational Organic Chemistry, pp. 520-521 (Preparation of Aldol Condensation Products; note procedural changes!); 847-848 (Planning an Experiment) Also: Review Basic Operations from previous experiments, specifically 665-673 (Thin-Layer Chromatography), 656-664 (Liquid-Solid Column Chromatography), 773-792 (Infrared Spectroscopy; also refer to pp.793-801 for Characteristic Infrared Bands), 802-815 (Nuclear Magnetic Resonance Spectrometry) PRELAB: In your lab notebook, write the following information before coming to lab: ü Balanced equation for the aldol condensation; ü Mechanism for the aldol condensation; ü Calculate the amounts you will need of your starting materials (based on 3.0 mmol

limiting reagent); ü Theoretical yield for final product (based on 3.0 mmol limiting reagent); ü Table of reagents containing all starting materials and products, with the data for all

pertinent physical properties (MW, bp/mp, density, etc.);

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PROCEDURE: • Obtain 3 mmol of 3’-methoxyacetophenone and 3 mmol of 4-

methylbenzaldehyde (also called p-tolualdehyde). Dissolve in 30 mL methanol and add 3 mL 3M NaOH.

• Stir the solution vigorously under reflux conditions until the reaction is complete (monitor by TLC).

• When the reaction is complete, cool the solution to room temperature and remove the solvent via rotary evaporator.

• Add 40 mL methylene chloride and 10 mL H2O to the residue. Transfer to a separatory funnel, shake, and separate the layers. If the layers do not separate, add 5 mL saturated NaCl.

• Wash the organic layer with saturated NaCl (2 x 10 mL), dry over MgSO4, and evaporate the solvent.

• Purify the product by column chromatography. Use your TLC to determine an appropriate eluent.

LAB REPORT: Follow the Lab Report Guidelines included with this syllabus. Report should include: ü Balanced equation for aldol condensation for your derivative; ü Mechanism of aldol condensation; ü Calculate percent yield (experimental yield/theoretical yield * 100%) for all products ü Fully interpret the data on both the IR and NMR spectra, and include both printouts

with your report ü Explain in detail how you purified your product (include TLC data if necessary) ü Based on your data, comment on the purity of your product ü Discuss in detail any problems you encountered during the experiment and how you

dealt with them QUESTIONS: A handout will be given to you containing the postlab questions for this experiment. Use complete sentences to answer the questions. Any structures and mechanisms should be drawn with appropriate software, not hand-drawn. The assigned readings are usually an excellent place to being searching for answers. Make sure that your answers to the postlab questions are included at the end of your postlab report.

chem237labmanual fall2012 r

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