Question

Match the reactions in List I with the final products formed as given in List II.

• A. W - R, X - S, Y - P, Z - Q
• B. W - R, X - P, Y - Q, Z - S
• C. W - S, X - R, Y - Q, Z - P
• D. W - Q, X - P, Y - S, Z - R

Hint:

Remember the following reagent selectivities:
• DIBAL-H reduces esters to aldehydes.
• Organocadmium reagents convert acid chlorides into ketones.
• Grignard reagent + nitrile followed by hydrolysis gives ketone.
• Controlled oxidation of toluene can produce benzaldehyde. These reactions are extremely important for board examinations and competitive entrance examinations.

Answer 1

The Correct Option is A

Concept: This question is based on important name reactions and reagent selectivity in Organic Chemistry. The reactions involve oxidation, controlled reduction, nucleophilic addition using Grignard reagent, and preparation of ketones from acid chlorides. Knowledge of how specific reagents behave toward functional groups is essential to solve this problem correctly.

Step 1: Analysis of Reaction W The starting compound is toluene: \[ \mathrm{C_6H_5CH_3} \] The reagent used is: \[ \mathrm{CrO_3 + (CH_3CO)_2O} \] Chromium trioxide in acetic anhydride performs controlled oxidation of the methyl group attached to the benzene ring. Initially, a gem-diacetate type intermediate is formed. On acidic hydrolysis and heating: \[ \mathrm{(ii)\ H_3O^+ + heat} \] the intermediate converts into benzaldehyde. Thus, the final product obtained is: \[ \mathrm{C_6H_5CHO} \] which corresponds to R. Therefore: \[ W \rightarrow R \]

Step 2: Analysis of Reaction X The substrate is an ester: \[ \mathrm{RCOOC_2H_5} \] The reagent used is DIBAL-H (Diisobutylaluminium hydride). DIBAL-H is a very important selective reducing agent. Under controlled low temperature conditions, it reduces esters only up to the aldehyde stage and prevents further reduction to alcohol. Hence: \[ \mathrm{RCOOC_2H_5 \xrightarrow[DIBAL-H]{} RCHO} \] Thus, the product formed is aldehyde: \[ \mathrm{RCHO} \] which corresponds to S. Therefore: \[ X \rightarrow S \]

Step 3: Analysis of Reaction Y The substrate is nitrile: \[ \mathrm{RCN} \] Nitriles react with Grignard reagent: \[ \mathrm{R-Mg-X} \] in dry ether. The Grignard reagent attacks the electrophilic carbon atom of the nitrile group producing an imine magnesium salt intermediate. Upon acidic hydrolysis: \[ \mathrm{H_3O^+} \] the imine converts into ketone. Thus: \[ \mathrm{RCN \xrightarrow[R-Mg-X]{H_3O^+} R_2CO} \] Hence, the product formed is ketone: \[ \mathrm{R_2CO} \] which corresponds to P. Therefore: \[ Y \rightarrow P \]

Step 4: Analysis of Reaction Z The substrate is benzoyl chloride: \[ \mathrm{C_6H_5COCl} \] It reacts with dimethyl cadmium: \[ \mathrm{(CH_3)_2Cd} \] Organocadmium compounds are less reactive than Grignard reagents. Therefore, they react with acid chlorides to form ketones and stop at that stage without further addition. The reaction produces acetophenone: \[ \mathrm{C_6H_5COCH_3} \] which corresponds to Q. Therefore: \[ Z \rightarrow Q \] Final Matching: \[ W \rightarrow R \] \[ X \rightarrow S \] \[ Y \rightarrow P \] \[ Z \rightarrow Q \] Hence, the correct answer is: \[ \boxed{(A)} \]