2-Methyl-1,1-diphenylpropane-1,2-diol, $(C X_{6} H X_{5}) X_{2} C (OH) - C (OH) (CH X_{3}) X_{2}$ , is treated with dilute $H X_{2} SO X_{4}$ (pinacol rearrangement). The ionisation occurs at the carbon that gives the more stable cation, followed by migration of a group from the neighbouring carbon. The major product is

A2-methyl-1,2-diphenylpropan-1-one
B3,3-diphenylbutan-2-one
C1,1-diphenylpropan-2-one
D3,3-diphenylbutan-2-ol

Answer: B

Loss of the OH on the diphenyl carbon gives the diphenylmethyl-type cation, which is better stabilised than the tertiary dimethyl cation. A methyl group then migrates from the carbinol carbon, which becomes

C = O

. The result is

CH X_{3} - CO - C (CH X_{3}) (C X_{6} H X_{5}) X_{2}

, 3,3-diphenylbutan-2-one.

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Answer: B

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