Which of the following diols give a ketone (and not an aldehyde) as the major product on treatment with dilute $H X_{2} SO X_{4}$ and heat?

A1,1-diphenylethane-1,2-diol
B2-methylpropane-1,2-diol
Cpinacol, $(CH X_{3}) X_{2} C (OH) - C (OH) (CH X_{3}) X_{2}$
D2,3-diphenylbutane-2,3-diol

Answer: C, D

A ketone results when the carbon that finally becomes C=O carried two carbon substituents besides OH. Pinacol and 2,3-diphenylbutane-2,3-diol have two such fully substituted carbinol carbons and give ketones. The other two diols have a

CH X_{2} OH

end, which becomes

CHO

after hydride migration, so they give aldehydes.

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Which of the following diols give a ketone (and not an aldehyde) as the major product on treatment with dilute HX2​SOX4​ and heat?

Answer: C, D

More questions on Pinacol-pinacolone and related rearrangements

Which of the following diols give a ketone (and not an aldehyde) as the major product on treatment with dilute $H X_{2} SO X_{4}$ and heat?