Salicylic acid

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Name Systematic name Formula Melting point Boiling point Color Structure
salicylic acid 2-hydroxybenzoic acid C6H4(OH)CO2H 159°C
acetylsalicylic acid
2-acetoxybenzoic acid C6H4(OCOCH3)CO2H

Salicylic acid

A colorless, crystalline organic carboxylic acid. It is usually prepared by Kolbe synthesis (aka Kolbe-Schmitt reaction), which works by heating sodium phenolate (the sodium salt of phenol) with carbon dioxide under pressure (100 atm, 125°C), then treating it with sulfuric acid. Salicylic acid is also found in plants, especially in fruits, in the form of methyl salicylate.  It is toxic if digested in large quantities, but in small quantities used as a food preservative and antiseptic in toothpastes. The carboxyl group (-COOH) can react with alcohols, forming several useful esters. The hydroxyl group (-OH) can react with acetic acid to acetylsalicylic acid.

Acetylsalicylic acid (Aspirin)

Acetylsalicylic acid can be prepared by the esterification of the phenolic hydroxyl group of salicylic acid. It is used in medicine as an analgesic, as an anti-inflammatory agent, and as an antipyretic compound.