Analgesics are compounds used to reduce pain, antipyretics are compounds used to reduce fever. One popular drug that does both is aspirin. Salicylic acid is reacted with acetic anhydride with the use of heat and sulfuric acid, which acts as a catalyst, to produce acetylsalicylic acid or commonly known as aspirin. This process is known as esterification. In the experiment, 2.0293 g of salicylic acid is used to react with 4.00 ml of acetic anhydride to produce 0.3565 g of acetylsalicylic acid giving rise to a 13.45 % yield.
             Salicylic acid is a simple aromatic carboxylic acid that became a key component of medical treatment throughout history, dating back to the Greeks (400 BC) and their use of willow tree bark. It was found in 1827 that the active agent in willow bark is an aromatic compound called salicin, which could be converted by reaction with water into salicyl alcohol and then oxidized to give salicylic acid.
             Felix Hoffman, working for Friedrich Baeyer and Company in 1883, acetylated salicylic acid and reduced the irritating side effects of salicylic acid in the mucous membrane of the stomach and made one of history's most popular drugs commonly referred to as aspirin (acetylsalicylic acid). Aspirin proved to be more effective in relieving pain and inflammation of rheumatoid arthritis.
             In a search for even more effective and less irritating analgesics and anti-inflammatory drugs, the Boots Pure Drug Company in England discovered ibuprofen. Soon thereafter, Syntex Corporation in US developed naproxen and RhÔne-Poulenc in France developed ketoprofen.
             In the 1960's, it was discovered that aspirin acts as by inhibiting cyclooxygenase (COX), a key enzyme in the conversion of arachidonic acid to prostaglandins. The acetyl group of aspirin is transferrable to enzymes such as prostaglandin synthase. Acetylation of prostaglandin synthase inhibits its cyclooxygenase acti
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