Diphenylmethane is an organic compound with the formula (often abbreviated ). The compound consists of methane wherein two hydrogen atoms are replaced by two phenyl groups. It is a white solid.
Diphenylmethane is a common skeleton in organic chemistry. The diphenylmethyl group is also known as benzhydryl.
It is prepared by the FriedelâÂÂCrafts alkylation of benzyl chloride with benzene in the presence of a Lewis acid such as aluminium chloride:
The methylene group in diphenylmethane is mildly acidic with a pK of 32.2, and so can be deprotonated with sodium amide.
The resulting carbanion can be alkylated. For example, treatment with n-bromobutane produces 1,1-diphenylpentane in 92% yield.
Alkylation of various benzhydryl compounds has been demonstrated using the corresponding alkyl halides, both primary (benzyl chloride, ò-phenylethyl chloride, and n-octyl bromide) and secondary (benzhydryl chloride, ñ-phenylethyl chloride, and isopropyl chloride), in yields between 86 and 99%.
The acidity of the methylene group in diphenylmethane is due to the weakness of the , which has a bond dissociation energy (BDE) of . This is well below the published bond dissociation energies for comparable bonds in propane, where the BDE of is , and toluene, where the BDE of is .