Aspirin synthesis

Synthesis of Aspirin from Salicylic Acid

1. Preparation of Aspirin from Salicylic acid Mrs Chanda Ranjan Department of Pharmaceutical Chemistry The Oxford College of Pharmacy, Bangalore

2. Learning outcome 1. How Aspirin is synthesized in the laboratory? 2. Calculation of the practical yield.

3. Content: Materials Required. Principle Procedure Calculation Report.

4. Chemically Aspirin is 2-Acetoxybenzoic acid. 2. Aspirin is an effective analgesic (pain reliever), antipyretic (fever reducer) and anti-inflammatory agent and is one of the most widely used non-prescription drugs. 1. Salicylic acid contains a phenol group, and phenols are known to be irritating. 2. Due to this the phenol group was replaced with acetyl group that become (acetylsalicylic acid, also known as aspirin) which was shown to be much less irritating than salicylic acid. Preparation of Aspirin from Salicylic acid Chemicals Required : Salicylic acid, acetic anhydride, conc Sulphuric acid, Ethanol. Apparatus Required: Beaker, Funnel, Stirrer, Pipette Materials Required

5. Aspirin can be made by reacting salicylic acid with Acetic anhydride in the presence of an acid catalyst. This reaction is an example of Esterification reaction. The OH group (phenol group) on the salicylic acid forms an acetylated product with the acetic anhydride. 3. Salicylic reacts with acetic anhydride and with the aid of acidic condition the acetate ion detaches from the acetic anhydride and gets attached to the hydrogen ion released from the phenolic OH group and forms Acetic acid as the byproduct. 5. And the hydrogen ion of phenolic OH is replaced with Acetyl group resulting the formation of Aspirin Preparation of Aspirin from Salicylic acid Principle 4. The Acetic acid formed as the byproduct is washed with water and the remaining acetic anhydride also reacts with water to form acetic acid and then washed with water

6. Procedure 10 gm of salicylic acid, 14 ml of acetic anhydride, and 2 ml of concentrated sulphuric acid was taken in a beaker and heated over the water bath for half an hour at 60 to 65 degree C with continuous stirring 10 gm Salicylic acid 14 ml acetic anhydride 2ml conc Sulphuric acid Cold Water 2. After heating the mixture was poured into the cold water with occasional stirring. Preparation of Aspirin from Salicylic acid Water bath

7. 3. After some time the crude Aspirin was filtered. Crude aspirin 30 ml Ethanol + Crude Aspirin Warm water 4. The product will be dissolved in alcohol for recrystallization 5. After that it will be poured into warm water so that the solid separates Preparation of Aspirin from Salicylic acid Procedure

8. Cold Water Aspirin 6. The separated solid will be filtered and dried and after that its weight and melting point determination will be done. Preparation of Aspirin from Salicylic acid White, Crystalline Solid melting point - 136 °C boiling point - 140 °C .

9. Calculation Molecular weight of Salicylic acid = 138 gm Molecular weight of Aspirin= 180 gm 138 gm of salicylic acid gives  180 gm of Aspirin Therefore, 10 gm of salicylic acid will give  180 x 10 = 13.04 gm of Aspirin ________ 138 Theoretical yield = 13.04 gm Practical yield= ________ gm Percentage yield= Practical Yield x 100 ___________________ Theoretical yield Preparation of Aspirin from Salicylic acid

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