Benzoic acid

Benzoic Acid is a colorless crystalline solid and a simple aromatic carboxylic acid. It has the chemical formula C₇H₆O₂. The name is derived from gum benzoin, which was for a long time its only known source. Benzoic acid occurs naturally in many plants and it serves as an intermediate in the biosynthesis of many secondary metabolites.

History

Benzoic acid was discovered in the sixteenth century. The dry distillation of gum benzoin was first described by Nostradamus (1556), and then by Alexius Pedemontanus (1560) and Blaise de Vigenère (1596).

Properties

Benzoic acid is a weak acid, stronger than the fatty acids, susceptible to oxidation, and reactive with bases to form salts. It is lipophilic and tends to accumulate in fatty tissues.

Production

Commercially, benzoic acid is produced by partial oxidation of toluene with oxygen. The process is catalyzed by cobalt or manganese naphthenates. The process uses cheap raw materials, proceeds in high yield, and is considered environmentally friendly.

Uses

Benzoic acid is mainly consumed in the production of phenol by oxidative decarboxylation at 300−400 °C. The temperature required can be lowered to 200 °C by the addition of catalytic amounts of copper(II) salts. The phenol can be converted to cyclohexanol, which is a starting material for nylon synthesis.

Safety

Benzoic acid and its salts are generally recognized as safe (GRAS) by the Food and Drug Administration (FDA). They are used as food preservatives, with an E number of E210.

See also

• Sodium benzoate
• Benzoin resin
• Terephthalic acid
• Phthalic acid