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Chemistry 354Organic Chemistry Laboratory I
SafetyThe organic chemistry safety presentation on the web is available on the web at the following address: http://atom.chem.wwu.edu/dept/osafety/index.htm. Read pp 542 558 in the lab book. We administer the safety quiz online at the following URL:http://argon.chem.wwu.edu/SafetyQ/OCQLink.htm A link to the safety quiz is included at the bottom of the instruction page.
You will have 30 minutes to complete the 25 question quiz.
SafetyFirst Try: Tuesday, June 20, 8AM to Friday, June 23, 10AM
Second Try: Tuesday, June 20, 8:00 AM to Friday, June 23, 10 AM
Third Try: Tuesday, June 20, 8:00AM to Friday, June 12, 10 AM
In order to be enrolled in this course, each student will be required to take and pass a laboratory safety quiz. You must pass the quiz before Tuesday, April 6th at NOON. If you cannot successfully pass the quiz, you will be dropped from this course.
Chemistry 354 LecturePurpose: To ensure that each student, regardless of laboratory section and instructor, receives the same information in preparation for the experiment. Examinations: The midterm and final examinations will be given in this lecture session.
Introduction to Microscale LaboratoryRead: Experiment 1 (pp. 2 13)Technique 1 (pp. 542 558)Technique 2 (pp. 558 565)Technique 3 (pp. 566 573)Technique 4 (pp. 574 580)
Introduction to Microscale LaboratoryMacroscale: Quantities of chemicals on the order of 5 to 100 grams. Glassware containers up to 500 mL. Microscale: Quantities of chemicals on the order of 0.050 to 0.100 grams. Glassware containers up to 25 mL.
Introduction to Microscale LaboratoryHeatingNo flamesDispensing of liquidsAssignment:Laboratory exercise 1 (parts A and B)Laboratory exercise 2There is no pre-lab or laboratory report required for this assignment-
Experiment 2: SolubilityReading AssignmentExperiment 2 (pp.13 20)Technique 5 (pp. 581 589)Technique 10 (pp. 637 646)
NOTE: You will be expected to submit a pre-lab assignment before you begin this experiment!Consult the syllabus for your laboratory section for the due date for the pre-lab exercise and for the final laboratory report.
SolubilityThe extent to which a substance is soluble in a solvent. Examples (solubility in water at 25C):Cholesterol 0.002 mg/mLCaffeine22 mg/mLCitric acid620 mg/mL
Solubility -- DefinitionsSolute: The substance that is being dissolved Solvent: The medium in which the solute is being dissolved. NOTE: In a solution, the solvent molecules greatly outnumber the solute molecules.
If a liquid organic compound is dissolved in a solventMiscible: solute and solvent mix homogeneously in all proportions Immiscible: solute and solvent do not mix; they form two separate liquid phases
Part A: Solubility in a Series of Solvents
Some hints on doing the solubility lab:
You can do the various parts of the experiment in any order you wish! This eliminates lineups by the Balances. Part A is especially time consuming!
Be sure to approximate the amounts of solids you are using in Part A. You dont need to be exact on the weights.
You will study the solubility behavior of benzophenone, malonic acid, and biphenyl in: Water, methanol, hexane How does the polarity of the solute influence the solubility in each of these solvents? What factors are at play, here?
Make a guess as to the solubility of malonic acid inwater. Notice that the acid has two very polar carboxylgroups in the compound. Would you expect this compound to be soluble inthe non-polar hexane solvent?
How consider the solubility of biphenyl in water. Make a guess as to the whether it will be soluble in water.What about the solubility in hexane?
Solubility RuleLike Dissolves Like
Why Does The Rule Work?If a substance is to dissolve in a solvent, the intermolecular attractions between solute molecules and solvent molecules must be similar in strength as the solute-solute and solvent-solvent intermolecular attractions.
Types of Intermolecular AttractionsDipole-dipole attractions
Hydrogen-bonding Van der Waal (London) forces
Part B. Solubility of Different AlcoholsSolutes:
All three of these alcohols have a polar hydroxylgroup. However, the rest of the molecule has a non-polar hydrocarbon chain.
How does the length of the carbon chain influence the solubility of the test alcohol in water?
How does the length of the carbon chain influence the solubility of the test alcohol in hexane?
What accounts for any differences?
Part C. Miscible or Immiscible PairsHere we examine pairs of compounds to determine whether or not they are miscible (soluble).How do differences in polarity affect solubility?How do intermolecular attractions influence the solubility of a solute in a particular solvent?
Part D. Solubility of Organic Acids and BasesSolutes:
What is the important component in 1.0 M NaOH? What is the important component in 1.0 M HCl?
What principle explains the solubility of a substance in aqueous acid or aqueous base?
Many covalent organic molecules are not very soluble in water even if they are somewhat polar! Benzoic acid is an example.
When benzoic acid is reacted with sodium hydroxide, it is converted to an ionic substance (sodium salt), The ionic substance is now much more soluble in water! Ionic substances are very polar!
When benzoic acid reacts with sodium hydroxide, what happens to the covalent molecule?
Ionic compounds are soluble in water!Benzoic acid is converted to an ionic compound!
Compounds with amino groups are basic. Theywill become ionic when reacted with an acid becausethe lone pair on the nitrogen atom becomes bondedto a proton which creates an ionic substance.
So, what would you expect for the behavior of ethyl 4-aminobenzoate in acid solution and basic solution?
Remember ThisIonic compounds are usually very soluble in water. Consider Na+ Cl-Higher molecular weight compounds with covalent bonds are usually insoluble in water If the covalent compound can be converted to ions, it will dissolve in aqueous solution!
Part E. Critical Thinking ApplicationSkip this section
Experiment 3: CrystallizationReading Assignment:Experiment 3 (pp. 21-32)Technique 6 (pp. 589-597)Technique 7 (pp. 598-616)Technique 8 (pp. 616-627)Technique 9 (pp. 627-637)Technique 11 (pp. 647-668)
Experiment 3Note that this is a two-day experimentPlan on using your time as follows, or as your instructor suggests:First day: Part A and part BSecond day: Part C
Experiment 3NOTE CAREFULLY:Although the textbook does not say to submit your samples with your laboratory report, the laboratory report sheet does!Be sure to submit your purified samples of sulfanilamide and fluorene in separate labeled vials.
Experiment 3If you do not obtain 150 mg of sulfanilamide crystals for Part A or 45 mg of crystals for Part B, expect to repeat the procedure until you get it right.The key is to figure out how to get crystals to form using the minimum amount of solvent.
Experiment 3There is a pre-lab exercise that is due to your instructor before beginning this experiment. The 4th edition of the textbook doesn't have the data for sulfanilamide (although you could guesstimate from the graph on page 648, figure 11.2). Use the following data, instead:0 deg -- solubility 14 mg/mL20 deg -- solubility 24 mg/mL40 deg -- solubility 46 mg/mL60 deg -- solubility 88 mg/mL78 deg -- solubility 210 mg/mL
Consult your sections syllabus for the due date for post-laboratory report.
Remember to submit the samples with your laboratory report!
Part A. Semimicroscale CrystallizationUse an Erlenmeyer flask and Hirsch funnelPart B. Microscale CrystallizationUse a Craig tubePart C. Selecting a Solvent to Crystallize a SubstancePart D. Critical Thinking ApplicationSkip this section
Semimicroscale crystallization using vacuum filtration: Part A
Microscale crystallization using a Craig Tube: Part B
Craig Tube + Centrifuge Tube
Solubility Types of SolutionsSaturated: The solution contains the maximum amount of solute that it can hold at that temperature. No more solute can be dissolved. Unsaturated: The solution contains less than the maximum amount of solute that it can hold at that temperature. More solute can be dissolved. Supersaturated: The solution contains more solute than the maximum amount of solute that it can hold at that temperature. A supersaturated solution is unstable; a precipitate (or crystals) is likely to form if the solution is disturbed.
Crystal FormationA dissolved material will separate from the solution as it is cooled.If the crystal growth is slow and selective, that is crystallizationIf the crystal growth process is rapid and nonselective, that is precipitation.In crystal growth, molecules arranged themselves into a highly specific structure called a crystal lattice.
Crystal FormationA successful crystallization depends on a large difference between the solubility of a material in a hot solvent and its solubility in the same solvent when it is cold.A material can be purified by crystallization when both the desired product and the impurity have similar solubilities, but only when the impurity represents a small fraction of the total solid.