Experiment # 8:

Preparation of Aspirin

Date: 14-12-10

Muhammad Usman

(2008-chem-02-B)

Pyridine:

Harmful: Pyridine is harmful if inhaled, swallowed or absorbed through the skin.

Highly flammable: It has a flash point of 21

oC. It can readily catch fire. So care should be taken

while handling it. However, pyridine itself is weak carcinogen.

Properties of Pyridine:

IUPAC Name Pyridine

Other names

Azabenzene

Azine

py

Appearance Colorless liquid

Structure

Molecular formula C5H5N

Molar mass 79.1g mol-1

Density 0.9819g ml-1

Melting point -41.6oC

Boiling point 115.2 oC

Solubility in water Miscible

Auto-ignition temperature 21 oC

Salicylic acid:

Harmful:

It is a Harmful compound & can cause hearing loss in Zinc deficient

individuals.

Properties of salicylic acid:

IUPAC name 2-hydroxy Benzoic acid

Other names Salicylic acid

Structure

Molecular formula C7H6O3

Molar mass 138.12 g/gmol

Appearance Colorless crystaline organic

acid

Density 1.443 g/cm3

Melting point 159 oC

Boiling point 211 oC

Solubility in water 0.2 g/100 ml H2O (20 oC)

Acidity (Pka) 2.97

Flash point 157 oC

Acetyl-chloride:

Harmful: Eyes and skin is specially damaged with acetyl chloride. It can cause pain &

vomiting. It also reacts hazardously with ethanol and phosphorus tri-chloride.

Highly flammable: It has a flash point of 13

oC. It can readily catch fire. So care should be taken

while handling it because its combustion products include Acetaldehyde which is

a strongly carcinogenic substance. However, ethanol itself is not cancer causing.

Corrosive: Acetyl chloride is a corrosive compound. It burns eyes and causes blistering on

skin.

Properties of Acetyl chloride:

IUPAC Name Acetyl chloride

Other names Ethanoyl chloride

Acyl chloride

Appearance Colorless liquid

Structure

Molecular formula CH3-CO-Cl

Molar mass 78.49g mol-1

Density 1.104 g ml-1

Melting point -112 oC

Boiling point 52 oC

Solubility in water Reacts with water

Auto-ignition temperature 390 oC

Water:

It is a non-hazardous compound.

Environmentally safe:

Water is an essential part of life. Life cannot be sustained without water.

Food & eatables contain some amount of water in them. It is a non-

hazardous compound.

IUPAC name Water

Oxidane

Other names

Hydrogen oxide

Dihydrogen monoxide

Hydrogen monoxide

Hydroxylic acid

Hydrogen hydroxide

R-718

Oxygen dihydride

Oxygen hydride

Oxane

Structure

Molecular formula H2O

Molar mass 18.0152833 gmol-1

Appearance

Density

1000 kg m-3

(liquid)

917 kg m-3

(solid)

Melting point 0 oC

Boiling point 99.98 oC

Acidity (Pka) 15.74

Basicity (Pkb) 15.74

Viscosity 0.001 Pa.S (20 oC)

Preparation of Aspirin

Chemicals required:

1) Acetyl Chloride 2) Dry Pyridine 3) Salicylic acid 4) Water

Chemical reaction:

Apparatus Required:

Volumetric flask Weigh Balance

Wire Gauze Tripod stand

Filter paper Beaker

Stirrer

Procedure:

1. Place 10 g Salicylic acid in conical flask & added 7 ml of Pyridine. Finally added 7.5 ml of

acetyl chloride at a rate of 1 ml per unit time with shaking continuously.

2. The reaction was exothermic in nature. The heat of reaction is responsible for the rise in

temperature of the mixture. Maintain the temperature of the mixture between 50-60 oC.

3. Then the solution was heated on water bath for 5-10 minutes & then cooled. This mixture was

poured in 300 ml of cold water.

4. Solution was filtered and aspirin was dried as product.

Precautions:

1. Take special care to avoid fumes evolved during heating or use fuming hood while

heating.

2. Solution should be stirred continuously during heating.

3. Water bath should be used for heating purpose.

Uses of Aspirin:

Aspirin’s uses lie in the category of Drugs. Its uses in the form of drug are as follows.

Analgesic:

It is used to relieve minor aches and pains.

Antipyretic:

It is used to reduce fever.

Anti inflammatory:

Aspirin is also used as an anti-inflammatory drug.