experiments of organic chemistry

UUnniivveerrssiittyy ooff TTeecchhnnoollooggyy EExxppeerriimmeennttss iinn CChheemmiissttrryy CChheemmiiccaall EEnnggiinneeeerriinngg LLaabboorraattoorryy MMaannuuaall

DDeeppaarrttmmeenntt FFiirrsstt YYeeaarr

e-mail: [email protected] or [email protected] website: http://www.uotechnology.edu.iq/dep-chem-eng/index.htm

35

EExxppeerriimmeennttss ooff

OOrrggaanniicc CChheemmiissttrryy

UBy Dr. Manal A. Tooma Lec. Luma Hussein

Lec. Ass. Alyaa Esaam

Chemist. Malad Fadhel Biologist. Shaymaa Kadhem

Chemist.Wasan Samee

mailto:[email protected]%20or

mailto:[email protected]




36

UContents Page No. Exp. Name Exp. No.

Boiling point determination Exp. No. 1

Melting point determination Exp. No. 2

Simple Distillation Exp. No. 3

Preparation of aspirin Exp. No. 4

Preparation of ester Exp. No. 5

Identification of functional groups Exp. No. 6

Saponification reaction Exp. No. 7

Dyes& Colorants Exp. No. 8

Octane Number Exp.No.9






37

UBoiling point determination

The boiling point of liquid is a temperature at which the vapor pressure of the

liquid is equal to the external pressure exerted at any point upon the liquid

surface.

UProcedure:

1) Close one end of the capillary tube by the flame of a burner.

2) Place a small quantity of the liquid (0.5 ml) in boiling tube (4-5 mm diameter

and 80-90 mm length).

3) Invert the capillary tube (closed end up – ward) and introduce it with its open

end; down – ward inside the boiling tube (wider tube).

4) Attach the tube to thermometer by rubber band in such a way that the bottom

end of the boiling tube is at the middle of the thermometer bulb.

5) Immerse the thermometer in an oil bath and adjust its height through a cork –

clamp – stand assembly.

6) Heat gradually the oil bath by a burner ( or other heating source ); and notice

the slow escape of air bubbles from the end of the capillary tube ,but near the

boiling point of the liquid ,a rapid and continuous escape of air bubbles will be

observed.

7) Record the reading of the thermometer when the rapid and continuous stream

of air bubbles first escape from the capillary tube as boiling point of the liquid.






38

8) Now remove the heating source from oil bath, the speed at which the escaped

bubbles will slacken and finally, when the last bubble makes its appearance and

exhibits a tendency to suck back, read thermometer reading immediately, this is

the true and accurate boiling point of the liquid because it is the temperature at

which the vapor pressure of the liquid is equal to that of atmosphere.

UDiscussion :

1) What is the advantage of determination of boiling point?

2) Why oil bath is used?

3) Why the boiling tube must be clean and dry?

4) Which is higher boiling point linear chain or branch chain of hydrocarbons

compounds?

UMelting Point Determination

The melting point of crystal solid is the temperature at which the solid begins to change

into liquid under atmospheric pressure. For powder substance, the change from the solid

to the liquid state is quite sharp (within 0.5P

oPC).Hence the temperature is a valuable mean

for identification purposes and an important criterion of purity.

UProcedureU:

1- Close one end of the capillary using the flame of a Benzene burner.

2- Push the closed capillary into the powder sample and inter the powder into the

capillary tube and clean the outside of capillary with soft tissue, don't let the powder

height exceed (2-3)mm.






39

3- Attach the capillary tube to the lower end of thermometer in such a way that the

substance is at the level of the middle part of the mercury bulb using a rubber band.

4- Insert the attached capillary tube with thermometer to the center of an oil bath.

5- Hang the thermometer by a clamp fixed to stand and adjusts the height properly.

Read the changing in temperature.

6- Start the heating operation and slow down before reading the melting point range

temperature, at an approximate rate of 2P

oPC per minute until the compound melts

completely.

7- The temperature at which the substance starts to liquefy and the temperature at

which the salt has disappeared, the melting point range are observed and recorded.

For a pure compound, the melting point range should not exceed (0.5-1)P

oPC, it is

usually less.

UDiscussion U:

1- Define the melting point and what is the benefit of it?

2- What is the effect of impurities on melting point?

3- What is the bath type used for determination of melting point and why?

4- When you repeat the procedure, the oil bath must be cooled why?

5- Why the level of the capillary tube and the thermometer bulb should be the same?

6- Why the sample should be packed into the capillary tube and the height not more

than (2 - 3) mm height?






40

USimple Distillation

The purpose of this experiment is to separate a volatile liquid from a non-

volatile substance or, more usually the separation of two or more liquids of

different boiling points. This is usually called fractional distillation.

Ideal solution possessing the following properties:.

1- There is no heat effect when the components are mixed.

2- There is no change in volume when the solution is formed.

3- The vapor pressure of each component equal to the vapor pressure of the pure

substances multiplied by its mole fraction in the solution.

4- There is no chemical reaction between the components in the mixture.

Another purpose of such distillation is to purify one substance from impurities.

UProcedure 1) The distillation glass wear is shown in figure (3).

2) Introduce 100ml of mixture solution required to separate to its components

into the round bottomed flask with 2-3 pieces of boiling chips (stone).

3) Fix the thermometer and make sure that the running water is circulating in the

condenser.

4) Start the heating process and record the temperature, until mixture start to

boil.

5) Adjust the heating rate so that only 15-25 drops of condensed distillate is

collected per minute.

6) Continue recording the temperature, for every 5ml of distillate, until all the

mixture has been distilled.






41

7) Ensure the separation of two substances when there is a sharp increase of

temperature with lower rate of distillation.

Fig.(3) distillation glass wear

UResults: Sketch graph between Temp. (Y axis) and ml of volume distillate (X axis) and

determine:

1) Initial boiling point.

2) Final boiling point.

3) Percentages of mixture distilled.

Thermometer

Join Condenser

Flask

Heater

Open ends for water flowing

Receiving Flask






42

UPreparation of Aspirin

Acetyl salicylic acid known as "Aspirin" Acetylationis prepared by the

acetylation process of salicylic acid and anhydride in the presence of little

concentrate sulpheric acid as catalyst.

Salicylic acid (O-hydroxybenzoicacid) upon acetylation yields acetylsalicylic

acid or aspirin and acetic acid as shown in the reactions mechanism below.

OHCO

OH H3C CO

OH3C C

O

OCO

OHCO

CH3 CH3COOH+ +H2SO4

OH

COOHO

COOH

CO

CH3

+

H+

CH3CO

OCH3CO

CH3CO

OCH3CO

H

CH3 CO

OHCH3CO

H

O

COOH

CO

CH3- H+






43

UProcedure: 1) Weigh ( 2.5)g of dry salicylic acid and place it into a conical flask.

2) Add 3.5ml of acetic anhydride to the conical flask.

3) Then add 3 drops of conc. HR2RSOR4R and shake the reacting solution.

4) Heat the conical flask and its contents in a bath at 50-60 ̊̊ C with occasional

shacking for (15) minutes.

5) Let the solution cool and shake it frequently.

6) Add 35ml of distilled water to the mixture shake and filter through funneled

filter paper.

UPurification In order to purify Aspirin, the formed precipitate is dissolved in 5ml of hot

alcohol, diluted with 10ml of distilled warm water. The mixture is heated until all

aspirin dissolves. Filter the hot solution, and then let it cool gradually. A clean

and pure aspirin re-crystallizes and can be filtered off. Determine the yield

UResults Determine the yield in g.

Theoretical wt. of aspirin = 𝑀𝑀𝑀𝑀𝐴𝐴𝐴𝐴𝐴𝐴

𝑀𝑀𝑀𝑀𝑀𝑀 𝐴𝐴𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠× 𝑀𝑀𝑀𝑀𝐴𝐴𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠

UDiscussion 1) What is the benefit of adding conc. HR2RSOR4Rsolution?

2) Why filter paper must be washed after filtration?

3) Why the temp. shouldn't rise more than 60 ̊ C ?

4) Why we add 35ml of distilled water to the flask after cooling?

5) What are the other methods for preparing ester?






44

UEsters and Esterification Many of the Esters type RCOOR have pleasant odors, and are produced by the

reaction of alcohol and carboxylic acids with the loss of water, according to the

following equation:

R CO

OH+ R-OH R CO

OR + H2O

The following procedure illustrates the preparation of ethyl acetate ester and its

separation from the reaction medium by reacting acetic acid and ethyl alcohol in

the presence of conc. HR2RSOR4R:

The addition of sulfuric acid increases the rate of reaction towards equilibrium

but it doesn't affect the products yield.

UProcedure:

1- Pipette out 10ml ethyl alcohol to a 250 ml round bottomed flask containing

few boiling chips.

2- Add (7.5)ml acetic acid to the alcohol and shake.

3- Add (0.5)ml of concentrated sulphuric acid very slowly, swirling the flask

continuously.

4- Heat the mixture to the boiling temperature for 1hr.

5- Distill-off pure ester form the other contents of the reacting mixture at 120-

130 C maximum temperature.

6- Collect the formed ester and measure of yield in (m1).

H2SO4 CH3COOH + C2H5OH CH3COOC2H5 + H2O






45

UIdentification of organic Functional Groups

Several organic functional groups such as alcohols, Aldehydes, Ketones

and esters exhibit particular specific chemical reaction which is used to test for

the presence of the group, or better known as identification of organic

compounds .When these groups are reacted with a specific chemical reagent,

either a colored or colorless solution is formed.

A) Characterization of Unsaturated Aliphatic Compound.

Unlike the saturated hydrocarbons, unsaturated aliphatic hydrocarbons are

soluble in concentrated sulphuric acid and exhibits characteristic reactions with

dilute potassium permanganate solution and with bromine. (Bayer Test for

unsaturation).

A dilute solution of potassium permanganate will oxidize the alkene.

As the unsaturated hydrocarbon is oxidized, the permanganate ions are reduced,

with loss of the purple color and appearance of a brown ppt.of manganese

dioxide.

R CH

CH

R + 2KMnO4+ 4 H2O R C C ROH OH

H H+ 2 KOH + 2 MnO23 3

UProcedure:

1) Dissolve 0.2ml of the unsaturated aliphatic hydrocarbon in 2-3ml distilled

water or acetone in a test tube.






46

2) Add drop-wise I% potassium permanganate solution with continuous

shaking.

3) The discoloration of the pink color of KMnOR4 Rsolution and the formation of a

brown ppt. suggests the presence of unsaturated aliphatic hydrocarbon (i.e. a

double bond).

B) Reaction of Aldehydes and Ketones

Both Aldehydes and Ketones contain the carbonyl group, a general test for

carbonyl compounds will immediately characterize both classes of compounds.

The preferred reagent is 2, 4- Dinitrophenylhydrazine, which gives sparingly

soluble phenyl hydrazine with carbonyl compounds:

R C

O2N

NO2H2NHN+

O2N

NO2NH

NHR CHO

+ H2O

Phenyl hydrazine

R C

O2N

NO2H2NHN+

O2N

NO2NR'

NHR C O + H2OR'

UProcedureU:

1) Introduce 5ml of 2, 4 – Dinitrophenyl hydrazine into a test tube.

2) Add30-40 mg of aldehyde or ketone diluted in 0.5ml of methanol.

3) Shake the test tube until a product (or a precipitate) formed.

4) Otherwise heat the test tube with its contents and shake for 30 seconds until a

yellow-orange crystalline ppt. is formed.

5) A colored crystalline ppt. indicates the presence of carbonyl compounds.






47

C) Differentiation between Aldehydes and Ketones:

The chemical distinction test between Aldehydes and Ketones depends

upon the difference in the oxidation of the two classes of carbonyl compounds.

Although both Aldehydes and Ketones may be oxidized to acids, Ketones are

oxidized under more vigorous oxidizing conditions (i.e. stronger reagents and

higher temperatures).Aldehydes is readily oxidized under very mild conditions.

The principal oxidizing agents used in these tests are: Tollens reagent,

Benedict's solution, Schiff's reaction and Fehling test.

UTollens Reagent test:

This is an ammonia Cal solution of silver oxide. The reagent is reduced by

Aldehyde to metallic silver, (producing a silver mirror on the inside wall of the

test tube) and the Aldehyde is oxidized to the corresponding acid. Ketones do

not react with the reagent.

UReactions

U1)Preparation of Tollens ReagentU.

2AgNO3 + 2 NaOH Ag2O + H2O + 2NaNO3

Ag2O + 4 NH4OH 2Ag(NH3)2OH + 3H2O

2)U Reactions Test:

+R CO

2Ag + NH4OHH 2Ag(NH3)2OH R CO

O NH4 +






48

Notes: If the test for the carbonyl compound is negative, then the unknown is a

ketone.

UProcedure

1)Preparing the Reagent:

Add two drops of 10%sodium hydroxide to 1.0ml of 5%silver nitrate solution in

a test tube. Shake the test tube, then add dropwise diluted solution of ammonium

hydroxide slowly with continuous shaking until a product of silver hydroxide is

formed (a brown-gray precipitate of silver oxide just dissolves).

2) The test:

Add 50gm (or 0.5ml) of the unknown compound to a 2ml of freshly prepared

Tollens reagent in a test tube don’t shakes the tube, then let it stand for 15

minutes .If no reaction appear to have taken place, heat the test tube with its

contents in a water bath of 35P

oPC for 5 minutes. Let the reacting materials to cool

down, a silver mirror is formed at the bottom of the tube if aldehyde is present.

D) Reaction of Halogenated Hydrocarbons

Halogenated hydrocarbons are derivatives of a hydrocarbon where one or

more hydrogen atom has been replaced by a halogen (F, Cl, Br or I) designated

by the letter (X) with the general formula for alkyl halides as RX (mono halide

substitution).

+R CO

R' 2Ag(NH3)2OH N.R






49

AgX + RNOR3

An important reaction for the identification of alkyl halides is the formation of

colored precipitates for silver halide upon reaction with alcoholic solution of

silver nitrate .The alcohol serves as a common solvent for the silver nitrate and

the organic compound to be tested.

UProcedure

1) Add 30-40 mg of alkyl halide to 0.5 ml saturated ethanol solution of silver

nitrate.

2) A colored ppt. of silver halide must form within 2 minutes

3) Repeat the reaction with different halides and report the resulting color of ppt.

E) Reaction of an Ester:

Esters are also carboxylic compound with the general formula

They normally possess sweet odour. The most convenient chemical reaction

used to identify an ester is the hydroxamicacid test, by which the ester react with

hydroxylamine to form an alcohol and a hydroxamic acid, which in turn reacts

with ferric chloride in acidic medium forming colored (usually violet ) complex

salts :

RX + AgNO3 Ethanol

Colored ppt.. Alkyl

O ║ R – C – OR






50

+R CO

O R' H2NOH RCONHOH + R'OHKOH

3RCONHOH + FeCl3 (RCONHO)3Fe + 3HClHCl

UProcedure:

1) Introduce 0.5ml of IN hydroxylamine hydrochloride in methanol solution into

a clean test tube.

2) Add about o.25g of an ester to the above solution.

3) Then add (drop wise) few drops of 2N KOH solution until the solution

becomes basic to the litmus paper immersed in the reaction mixture.

4) Heat the tube with its contents to near boiling temperature, and let it cool.

5) Acidify the cooled mixture with few drops of 2N HCl solution (to litmus).

6) Then add 1ml of 10%ferric chloride solution.

7) Observed the violet complex salt of ferric formed.

USaponification Reaction (Soap)

The term fat is applied to solid esters of fatty acids, with glycerides); if the fat is

liquid at the ordinary temperature it is conventionally called fatty oil.

Saponification is the name given to alkaline hydrolysis of fats and oils to give

glycerol and the alkali metal salt of along chain fatty






51

CH2OOCR

CHOOCR

CH2OOCR

+ 3NaOH

CH2OH

CHOH

CH2OH

+3 RCOONa

CH3OOCR + 3NaOH CH3OH + RCOONa

The sodium and potassium soaps are soluble in water and are used as cleansing

agents.

UProcedure

1) Weight out 9gm of sodium hydroxide (NaOH) (on a watch glass).

2) Transfer the solid to a 250 ml conical flask and dissolve carefully in 40 ml of

distilled water.

3) Add 30 ml of vegetable oil (or fat) and heat with occasional shaking, for 30

minutes.

4) Remove the conical flask from the heater and allow cooling.

5) Transfer the reaction mixture into a 250 ml separating funnel.

6) Add 100 ml of saturated (sodium chloride NaCl in water and shake well for 3-

4 minutes.

7) Allow the separating funnel to stand for 3-4 minutes and until two distinct

layers separates out.

8) Separate the soap solution. Measure its volume and determine the yield. (Take

a small sample and shake well in a test tube with little tap water). let it dry then

report the weight.

Report your results with description of the above parameters.






52

UDiscussion

1) How soap formed?

2) Why sodium soap used as a cleaner?

3) Why we heat the reaction mixture for half an hour?

4) Why salt is added?

UDyes and Dyestuffs

Fast dyes are employed largely to fabrics among other materials for fixed

coloring purposes.

In this experiment, two types of dyes will be prepared.

UA) Organic Dyestuff:

UThe coupling of aromatic diazonium compounds:

Nearly one –half of all synthetic dyes now in use are dyes prepared by coupling

aromatic diazonium salts with phenols ,naphtha's or aromatic amines.

The coupling reaction is carried out in alkaline, neutral, or in weakly acidic

solution.

UProcedure:

(1) Introduce 0.1 of p- nitro aniline in a beaker (50 ml).

(2) Add13 ml of dilute hydrochloric acid solution, and shake until the solid dissolves.






53

(3) Place the beaker in an ice bath and cool to 0- 5 ̊C.

(4) In a test tube, dissolve 0.1g sodium nitrite NaNOR2Rin 5ml of distilled water.

(5) Carefully and slowly, add the above test tube contents to the cold p-nitro aniline

hydrochloride solution and shake gently the mixture .this is solution number (1).

The diazotization and coupling reactions takes place within the fabric at the

temperature of an ice bath. This method of dyeing is known as "Ingrain Dyeing".

NH2

NO2

NH3Cl

NO2

HCl

N2Cl

NO2

NaNO2

0.5 oC

In second test tube , dissolve 0.1g B-Naphthol.in 5ml solution sodium hydroxide .this is solution

NO(2).

(6) Insert a piece of white cloth solution No.(I) then in solution No.(2).

+ HCl

N2Cl

NO2

OH NO2N N+

(7) Describe the color developed on the inserted cloth, and report its fastness (degree of

fixation) by washing it with cold, hot water and other available solvents.

B U- Inorganic Dyestuffs U:

Inorganic dyestuffs can also be used to dye fabrics and other materials to a good

degree of fastness.

An example of such dye is the one prepared by the reaction between potassium

dichromate and lead acetate solutions, producing a fast yellow color dye with the

following reaction:






54

K2Cr2O7 + (CH3COO)2Pb PbCrO4 + 2CH3COOK + CrO3 Lead Chromate

Yellow

UProcedure: (1) Introduce 10ml f lead acetate solution into a 50ml beaker and heat the solution to

60-80̊C. this is solution No. (1).

(2) Introduce 10ml of potassium dichromate into a second 50ml beaker. This is

solution No. (2).

(3) Insert a piece of white cloth in solution No.(1) then in solution No.(2) and

proceed as for the previous experiment in preparing an organic dyestuffs.

UPreparation of acetic acid

Ethanol is a primary alcohol; it contains hydroxyl group which at oxidation give

acetaldehyde first and then acetic acid. The oxidative agent (mixture of sodium

dichromate and sulfuric acid) is used for the preparation of acetic acid.

CH3CH2OH CH3CH(OH)2

CH3CHO

CH3CO

OHO - 2H

H2O

Aqueous ethanol was added gradually to the hot mixture of aqueous solution of

sodium dichromate and sulfuric acid.






55

UProcedure 1. Add 10ml of distilled water in around bottom flask, then add 3-5ml of

concentrated sulfuric acid with continuous stirring.

2. Add 3-5gm of sodium dichromate to the mixture and shake well to complete

dissolving.

3. Put in a separating funnel 1.5ml of alcohol with 6ml of water.

4. Add the mixture in the step (3) to the mixture in the step (2) with stirring

during addition (reflux).

5. Heat the mixture by using water bath for 20 minute.

6. Distill the mixture and collect 8ml of the distillate, which is acetic acid.

7. Make the following tests:

a- With litmus paper.

b- With sodium hydroxide.

c- With ethanol (Note smell ester ethyl acetate).

UDiscussion

1- Why was ethanol used?

2- Write the mechanism of the reaction?

3- Why was sodium dichromate added?

4- Why conc. sulfuric acid was slowly added?






56

UReferences:

1. J.D. Roberts,& M.C. Caseros, "Basic Principles of Organic

Chemistry", W.A. Benjamin,Ir c., New York, 1998.

2. G.W., Solomons, "Organic Chemistry", 4 P

thP Ed., John Wiely and

Sons, Inc., USA. 663, 1 (2001).

3. R.D., Hart, Scuet, " Organic Chemistry A Short Course " 5 P

thP Ed.,

Oughon Mifflin Comp., Boston.USA. 19, 26 (2001).

4. R.K. Bansal, "Organic Reaction Mechanism" 3 P

rdP Ed., (2000).

5. R.T. Morrlson, & R.N. Boyd,"Organic Chemistry", Inc., New

York, (2001).



experiments of organic chemistry

Documents