Synthesis and Characterization of Aspirin

Courtney Crowe

C127

Jordan Worcester

27 March 2015

Synthesis and Characterization of Aspirin

Objective:

Aspirin was synthesized from salicylic acid and acetic anhydride. Multiple tests were then preformed to determine how pure the sample was.

Introduction:

        Aspirin was formerly made from willows bark found by Ancient Egyptians. In fact, Hippocrates gave women willow bark to chew on to relieve the pain of childbirth2. This drug is currently one of the world’s greatest pain relievers. It is used to decrease pain, fever, and inflammation. They soon discovered that the salicylic acid caused stomach irritation. It was not until around 1860s when chemists developed a way of separating the pain-relieving chemical out of the willow bark.

        The first synthesis of aspirin began and chemists saw that they could create a compound that would reduce general pains without causing stomach irritation. The structure of salicylic acid contains a hydroxyl group along with a carbon ring.4 Felix Hoffman was able to change the structure of salicylic acid and replace the hydroxyl group with an acetyl group by reacting the salicylic acid with acetic anhydride, which contains the acetyl group. This new compound was known as acetylsalicylic acid and was later named aspirin. This compound reduced inflammation of the stomach and still relieved pain, inflammation and fever.

        After the synthesis of aspirin, qualitative tests were done to determine its purity. Since aspirin is sold to people in drug stores, chemists have to make sure it is purely only acetylsalicylic acid. One test to find its purity is finding its melting point. The melting point of pure acetylsalicylic acid should be within 1°C of its known melting point. The second test will utilize thin layer chromatography (TLC). Which also tests for the presence of salicylic acid or other products.  The final test, used iron salts to determine if the aspirin sample had residue containing salicylic acid.

Experimental Procedure:

Materials:

Water

Large Beaker

Hot Plate

1.959 g salicylic acid

Weighing boat

125 mL Erlenmeyer flask

4.0 g acetic anhydride

0.411 g sodium acetate

Ice

Beaker with 50-60 mL water

Dropper

Stirring rod

Buchner funnel

Filter flask

100 mL beaker

3 mL methanol

2 vials

2 rubber bands

2 cotton balls

3 melting point capillary tubes

Pure acetylsalicylic acid

Melting point apparatus

Glass jar with lib

Solvent [80:10:10 (hexane:ethanol:ethylactate)]

TLC plate

0.02 g aspirin

0.02 g pure acetylsalicylic acid