See image — Aldehydes Ketones and Carboxylic Acids Chemistry Question

💡 Solution & Explanation

Concept: The degree of hydration of a carbonyl compound (ketone) to form a gem-diol depends on the electrophilicity of the carbonyl carbon. More electron-withdrawing groups attached to the carbonyl carbon increase its electrophilicity, making it more susceptible to nucleophilic attack by water. Step 1: Identify the groups attached to the carbonyl carbon in each option. (a) CF3-CO-CF3: Two trifluoromethyl groups (CF3), which are strongly electron-withdrawing due to three fluorine atoms each. (b) CH3-CO-CH3: Two methyl groups, which are electron-donating. (c) CH3CH(Cl)-CO-CH3: One chloromethyl group (electron-withdrawing) and one methyl group (electron-donating). (d) C6H5-CO-C6H5: Two phenyl groups, which are electron-donating via resonance (lone pair donation into carbonyl) and also provide steric hindrance. Step 2: Rank electrophilicity of carbonyl carbon. - In (a), two CF3 groups withdraw electron density strongly from the carbonyl carbon through inductive effect, making it the most electrophilic. - In (c), one Cl-bearing carbon provides moderate electron withdrawal. - In (b), two methyl groups donate electrons, reducing electrophilicity. - In (d), two phenyl groups donate electrons via resonance and provide steric bulk, minimizing hydration. Step 3: Conclude which undergoes maximum hydration. Option (a) CF3-CO-CF3 (hexafluoroacetone) has the most electrophilic carbonyl carbon due to the strong -I effect of two CF3 groups. In fact, hexafluoroacetone is known to be nearly completely hydrated in water (>99%), forming the stable gem-diol (hexafluoroacetone hydrate). Why other options fail: - (b) Acetone is only slightly hydrated (~0.1%) because methyl groups donate electrons. - (c) Has only one moderately electron-withdrawing group, less effective than two CF3 groups. - (d) Benzophenone shows very little hydration due to resonance donation by phenyl groups and steric hindrance. Therefore, the correct answer is A.