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Salicylic acid

Name salicylic acid acetylsalicylic acid
Systematic name 2-hydroxybenzoic acid 2-acetoxybenzoic acid
Formula C6H4(OH)CO2H C6H4(OCOCH3)CO2H
Melting point 159C (318F)  
Boiling point 211C (412F)  
Color white, crystalline  

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, 125C), then treating it with sulfuric acid.

Salicylic acid is also found in plants, especially in fruit, 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 toothpaste. The carboxyl group (-COOH) can react with alcohols, forming several useful esters. The hydroxyl group (-OH) can react with acetic acid to acetylsalicylic acid.

Salicylic acid is the active ingredient in many skin-care products for the treatment of acne. It helps acne by causing skin cells to slough off more readily, preventing pores from clogging up.

Acetylsalicylic acid (Aspirin)

Acetylsalicylic acid (ASA) 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. It is sold under the brand name Aspirin by Bayer AG; see Aspirin for medical information.\n