Benzoic Acid

Abstract

Benzoic acid, C 6 H 5 COOH, is the simplest member of the aromatic carboxylic acid family. In the United States, virtually all benzoic acid is manufactured by the continuous liquid‐phase air oxidation of toluene. Benzoic acid and its salts and esters find application in medicinals, food and industrial preservatives, cosmetics, resins, plasticizers, dyestuffs, and fibers. Benzoic acid in the free state, or in the form of simple derivatives such as salts, esters, and amides, is widely distributed in nature. In its chemical behavior benzoic acid shows few exceptional properties; the reactions of the carboxyl group are normal, and ring substitutions take place as would be predicted. The growth of demand for benzoic acid is expected to increase at a rate of between 1 and 2% per year. Glycol dibenzoate plasticizers have been growing at close to 10% annually for several years, in part due to environmental concerns with regard to phthalate plasticizers. The growth of the diet soft drink market has increased the demand for sodium and potassium benzoates. All of the benzoic acid producers in the United States employ the liquid‐phase toluene air oxidation process. The bulk of benzoic acid production capacity is consumed internally by the producers. Kalama converts over half of its production to phenol. A large portion of Velsicol's benzoic acid production is utilized in the manufacture of glycol dibenzoate plasticizer esters. Benzoic acid is available in industrial and technical grades, and in grades meeting the specifications of the United States Pharmacopeia , the Food Chemicals Codex , or the British Pharmacopeia . Benzoic acid's toxicity is rated as moderate (3 on a scale of 1–6). Healthy individuals may tolerate small doses (under 0.5 g of benzoates per day) mixed with food without ill effects. The principal safety concern in handling molten benzoic acid is its elevated temperature. Thermal burns may result from improper handling of the molten product. Benzoic acid derivatives include benzoyl chloride (C 6 H 5 COCl), benzoic anhydride ((C 6 H 5 CO) 2 O), benzoic acid salts, and benzoic acid esters.