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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. 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 ...
When ortho substitution occurs in benzoic acid, steric hindrance causes the carboxyl group to twist out of the plane of the benzene ring. The twisting inhibits the resonance of the carboxyl group with the phenyl ring, leading to increased acidity of the carboxyl group.
One method involves its conversion to the Grignard reagent, phenylmagnesium bromide. This reagent can be used, e.g. in the reaction with carbon dioxide to prepare benzoic acid. [4] Other methods involve palladium-catalyzed coupling reactions, such as the Suzuki reaction. Bromobenzene is used as a precursor in the manufacture of phencyclidine.
Via the Hock rearrangement, cyclohexylbenzene hydroperoxide cleaves to give phenol and cyclohexanone. Cyclohexanone is an important precursor to some nylons. [8] Starting with the alkylation of benzene with mixture of 1 and 2-butenes, the cumene process produces phenol and butanones. [5]
The starting point for the collection of the substituent constants is a chemical equilibrium for which the substituent constant is arbitrarily set to 0 and the reaction constant is set to 1: the deprotonation of benzoic acid or benzene carboxylic acid (R and R' both H) in water at 25 °C. Scheme 1. Dissociation of benzoic acids
Birch reduction of benzene, also available in animated form. The reaction is known to be third order – first order in the aromatic, first order in the alkali metal, and first order in the alcohol. [4] This requires that the rate-limiting step be the conversion of radical anion B to the cyclohexadienyl radical C. Birch reduction of anisole.
Although of no commercial significance, many other routes to benzene exist. Phenol and halobenzenes can be reduced with metals. Benzoic acid and its salts undergo decarboxylation to benzene. The reaction of the diazonium compound derived from aniline with hypophosphorus acid gives benzene. Alkyne trimerisation of acetylene gives benzene.
Benzene can be easily converted to chlorobenzene by nucleophilic aromatic substitution via a benzyne intermediate. [1] It is treated with aqueous sodium hydroxide at 350 °C and 300 bar or molten sodium hydroxide at 350 °C to convert it to sodium phenoxide , which yields phenol upon acidification. [ 2 ]