See image — Aldehydes Ketones and Carboxylic Acids Chemistry Question

💡 Solution & Explanation

Step 1 - Concept: CrO2Cl2 (chromyl chloride) oxidizes toluene (Ph-CH3) via the Étard reaction to give an intermediate chromium complex. However, in this problem CrO2Cl2 converts Ph-CH3 into intermediate (A), which is benzaldehyde (Ph-CHO). This is the Étard oxidation product after hydrolysis, but here the hydrolysis step is replaced by treatment with conc. KOH. Step 2 - Identifying (A): CrO2Cl2 reacts with toluene to form the Étard complex, which upon mild hydrolysis gives benzaldehyde (Ph-CHO). So (A) = Ph-CHO (benzaldehyde). Step 3 - Reaction of (A) with conc. KOH: Benzaldehyde (an aldehyde with no alpha-hydrogen that can participate in aldol, but it can undergo Cannizzaro reaction) reacts with conc. KOH via the Cannizzaro reaction. In the Cannizzaro reaction, two molecules of an aldehyde lacking alpha-hydrogen undergo disproportionation: one molecule is oxidized to the carboxylate salt and the other is reduced to the alcohol. Step 4 - Cannizzaro reaction products: 2 Ph-CHO + KOH → Ph-CH2OH + Ph-CO2^- K^+ So the two products are benzyl alcohol (Ph-CH2OH) and potassium benzoate (Ph-CO2^-). Step 5 - Identifying (B): The problem states Ph-CH2OH is one product; therefore (B) must be Ph-CO2^- (benzoate anion / potassium benzoate). Step 6 - Why other options fail: - (a) Ph-CO2H: Under strongly basic (conc. KOH) conditions, the carboxylic acid would exist as its conjugate base (carboxylate), not as the free acid. So the direct product is Ph-CO2^-, not Ph-CO2H. - (c) Ph-CHO: This is the starting aldehyde (A), not a product. - (d) Ph-CH3: This is the original reactant toluene, not formed in this sequence. Therefore, the correct answer is B.