Benzoic acid occurs naturally in many plants<ref>{{#invoke:citation/CS1|citation
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In 1875 Salkowski discovered the antifungal properties of benzoic acid, which explains the preservation of benzoate-containing cloudberry fruits.<ref>Template:Cite journal</ref><ref>{{#invoke:citation/CS1|citation
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The first industrial process involved the reaction of benzotrichloride (trichloromethyl benzene) with calcium hydroxide in water, using iron or iron salts as catalyst. The resulting calcium benzoate is converted to benzoic acid with hydrochloric acid. The product contains significant amounts of chlorinated benzoic acid derivatives. For this reason, benzoic acid for human consumption was obtained by dry distillation of gum benzoin. Food-grade benzoic acid is now produced synthetically.
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.
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. This process usually gives a yield of around 65%.<ref>Template:Cite book</ref>
By hydrolysis
Like other nitriles and amides, benzonitrile and benzamide can be hydrolyzed to benzoic acid or its conjugate base in acid or basic conditions.
From Grignard reagent
Bromobenzene can be converted to benzoic acid by "carboxylation" of the intermediate phenylmagnesium bromide.<ref>Template:Cite book</ref> This synthesis offers a convenient exercise for students to carry out a Grignard reaction, an important class of carbon–carbon bond forming reaction in organic chemistry.<ref>Template:Cite journal</ref><ref>Template:Cite book</ref><ref>{{#invoke:citation/CS1|citation
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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.
Precursor to plasticizers
Benzoate plasticizers, such as the glycol-, diethyleneglycol-, and triethyleneglycol esters, are obtained by transesterification of methyl benzoate with the corresponding diol.<ref name=Ull/> These plasticizers, which are used similarly to those derived from terephthalic acid ester, represent alternatives to phthalates.<ref name=Ull/>
Precursor to sodium benzoate and related preservatives
Concern has been expressed that benzoic acid and its salts may react with ascorbic acid (vitamin C) in some soft drinks, forming small quantities of carcinogenic benzene.<ref>{{#invoke:citation/CS1|citation
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Template:See also
Medicinal
Benzoic acid is a constituent of Whitfield's ointment which is used for the treatment of fungal skin diseases such as ringworm and athlete's foot.<ref>{{#invoke:citation/CS1|citation
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}}</ref><ref>Template:Cite book</ref> As the principal component of gum benzoin, benzoic acid is also a major ingredient in both tincture of benzoin and Friar's balsam. Such products have a long history of use as topical antiseptics and inhalant decongestants.
Benzoic acid occurs naturally as do its esters in many plant and animal species. Appreciable amounts are found in most berries (around 0.05%). Ripe fruits of several Vaccinium species (e.g., cranberry, V. vitis macrocarpon; bilberry, V. myrtillus) contain as much as 0.03–0.13% free benzoic acid. Benzoic acid is also formed in apples after infection with the fungus Nectria galligena. Among animals, benzoic acid has been identified primarily in omnivorous or phytophageous species, e.g., in viscera and muscles of the rock ptarmigan (Lagopus muta) as well as in gland secretions of male muskoxen (Ovibos moschatus) or Asian bull elephants (Elephas maximus).<ref name = "concise" /> Gum benzoin contains up to 20% of benzoic acid and 40% benzoic acid esters.<ref>Template:Cite journal</ref>
It is excreted as hippuric acid.<ref>Template:Cite journal</ref> Benzoic acid is metabolized by butyrate-CoA ligase into an intermediate product, benzoyl-CoA,<ref name="Benzoic1">{{#invoke:citation/CS1|citation
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For humans, the World Health Organization's International Programme on Chemical Safety (IPCS) suggests a provisional tolerable intake would be 5 mg/kg body weight per day.<ref name="concise">{{#invoke:citation/CS1|citation
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}}</ref> Cats have a significantly lower tolerance against benzoic acid and its salts than rats and mice. Lethal dose for cats can be as low as 300 mg/kg body weight.<ref>Template:Cite journal</ref> The oral Template:LD50 for rats is 3040 mg/kg, for mice it is 1940–2263 mg/kg.<ref name="concise" />
In Taipei, Taiwan, a city health survey in 2010 found that 30% of dried and pickled food products had benzoic acid.<ref>Template:Cite news</ref>
