Diphenylmethane
Diphenylmethane is an organic compound with the formula . 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.
Synthesis
It is prepared by the Friedel–Crafts alkylation of benzyl chloride with benzene in the presence of a Lewis acid such as aluminium chloride:Reactivity of the C-H bond
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 and secondary, 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 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.