Butylated hydroxytoluene (BHT), also known as butylhydroxytoluene, is a lipophilic (fat-soluble) organic compound, chemically a derivative of phenol, that is useful for its antioxidant properties. European and U.S. regulations allow small percentages to be used as a food additive. While there may be some dispute in BHT's use in the human diet, the chemical is widely used in industry wherever oxidation in fluids (e.g. fuel, oil) and other materials must be treated, and free radicals must be kept in-check.
Production

BHT is prepared by the reaction of p-cresol (4-methylphenol) with isobutylene (2-methylpropene) catalyzed by sulfuric acid: [2]
CH3(C6H4)OH + 2 CH2=C(CH3)2 → ((CH3)3C)2CH3C6H2OH
Alternatively, BHT is prepared from 2,6-di-tert-butylphenol by hydroxymethylation or aminomethylation followed by hydrogenolysis.
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