A sequence of reactions is represented as : Benzene [Anhy. AlCl3] CH3Cl (A) [[O]] CeO2 H+ (B) [Reflux]alc. KCN (C) Predict the name of reaction that converts (B) to (C). a) Benzoin condensation b)…

The sequence of reactions involves benzene undergoing Friedel–Crafts alkylation with $\mathrm{CH}{}_3\mathrm{Cl}$ in the presence of anhydrous $\mathrm{AlCl}{}_3$ to form toluene (A).

benzenebenzeneAnhy. AlCl₃, CH₃Cltoluenetoluene

Next, toluene (A) is oxidized using $\mathrm{CeO}{}_2$ under acidic conditions ([O]) to yield benzaldehyde (B).

toluenetolueneCeO₂ | H⁺, [O]benzaldehydebenzaldehyde

In the final step, benzaldehyde (B) reacts with alcoholic potassium cyanide (KCN) under reflux. This reaction involves the nucleophilic addition of cyanide ion to the carbonyl group of benzaldehyde, followed by elimination of water to form an α,β-unsaturated nitrile. This specific reaction is known as the Perkin’s condensation when an aromatic aldehyde reacts with an acid anhydride in the presence of a strong base, but in this case, the reaction with alcoholic KCN is characteristic of the benzoin condensation only if two benzaldehyde molecules react. However, the correct transformation here is the nucleophilic addition-elimination leading to the formation of benzaldehyde cyanohydrin or related derivatives, but the closest named reaction among the options is Perkin’s condensation (though strictly, it is not a condensation here).

However, the correct named reaction for the conversion of benzaldehyde (B) to (C) (a nitrile derivative) under these conditions is not listed accurately. The closest plausible option is Perkin’s condensation, but the reaction is actually a nucleophilic addition of cyanide (not a condensation). If the question expects a condensation, the correct answer is Perkin’s condensation (option b), as it involves the formation of an unsaturated compound from an aromatic aldehyde under basic conditions.

Answer: b) Perkin's condensation (though strictly, the reaction is a nucleophilic addition, the closest named reaction is Perkin’s condensation).