Chemistry - STRUCTURAL ISOMERISM Question with Solution | TestHub

Trace base moves protons through an enediol : $\mathrm{Ph}-\mathrm{CH}(\mathrm{OH})-\mathrm{CO}-\mathrm{C}{\mathrm{H}}_3$ loses the carbinol alpha proton to give the enediol $\mathrm{Ph}-\mathrm{C}(\mathrm{OH})=\mathrm{C}(\mathrm{OH})-\mathrm{C}{\mathrm{H}}_3$, which re-ketonises at the other carbon to give $\mathrm{Ph}-\mathrm{CO}-\mathrm{CH}(\mathrm{OH})-\mathrm{C}{\mathrm{H}}_3$ (2-hydroxy-1-phenylpropan-1-one) - an isomer of (A). The other choices cannot result from simple proton shifts : they require moving the oxygen or the carbonyl along the chain (changes of connectivity of the carbon framework or of oxidation state). Hence (B) is $\mathrm{Ph}-\mathrm{CO}-\mathrm{CH}(\mathrm{OH})-\mathrm{C}{\mathrm{H}}_3$.