JEE Main · 2023 · 29 Jan 2023 · Shift 2 · Aldehydes Ketones and Carboxylic Acids

4${}^{\prime }$-Chloroacetophenone adds cyanide across its carbonyl group to give a cyanohydrin, and heating this nitrile with ethanol in acid converts the cyano group into an ethoxycarbonyl group while the hydroxyl is retained, so the first product is ethyl 2-(4-chlorophenyl)-2-hydroxypropanoate. When this $\alpha$-hydroxy ester is treated with an excess of methylmagnesium bromide, two methyl groups add to the ester carbonyl and, after acidic work-up, turn it into a tertiary alcohol, the hydroxyl already present being merely deprotonated and then regenerated. The second product is therefore 2-(4-chlorophenyl)-3-methylbutane-2,3-diol, in which the carbon bearing the aryl ring and the neighbouring carbon each carry a hydroxyl group.