Physical and chemical properties of benzoic acid


Benzoic acid was discovered in the 16th century. The dry distillation of gum benzoin first described by Nostradamus(1556), and subsequently by Alexius Pedemontanus (1560) and Blaise de Vigenère (1596).

Justus von Liebig and Friedrich Wöhler determined the composition of benzoic acid in 1832. They also investigated how hippuric acid is related to benzoic acid.

In 1875 Salkowski discovered the antifungal abilities of benzoic acid, which was used for a long time in the preservation of benzoate-containing cloudberry fruits.


Industrial preparations

Benzoic acid is produced commercially by partial oxidation of toluene with oxygen. The process is catalyzed by cobaltor manganese naphthenates. The process uses cheap raw materials, proceeds in high yield, and is considered environmentally green.[citation needed]

toluene oxidation

U.S. production capacity is estimated to be 126,000 tonnesper year (139,000 tons), much of which is consumed domestically to prepare other industrial chemicals.

Laboratory synthesis

Benzoic acid is cheap and readily available, so the laboratory synthesis of benzoic acid is mainly practiced for its pedagogical value. It is a common undergraduate preparation.

For all syntheses, benzoic acid can be purified by recrystallization from water because of its high solubility in hot water and poor solubility in cold water. The avoidance of organic solvents for the recrystallization makes this experiment particularly safe. Other possible recrystallization solvents include acetic acid (anhydrous or aqueous),benzene, petroleum ether, and a mixture of ethanol and water.

By hydrolysis

Like any other nitrile or amide, benzonitrile and benzamidecan be hydrolyzed to benzoic acid or its conjugate base in acid or basic conditions.

From benzaldehyde

The base-induced disproportionation of benzaldehyde, theCannizzaro reaction, affords equal amounts of benzoate andbenzyl alcohol; the latter can be removed by distillation.

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