Step 1: Understanding the Question:
The question asks to identify which of the given compounds will undergo the Cannizzaro reaction.
Step 2: Key Formula or Approach:
The Cannizzaro reaction is a specific chemical reaction with two key conditions:
1. The reactant must be an aldehyde.
2. The aldehyde must not have an \( \alpha \)-hydrogen atom. An \( \alpha \)-hydrogen is a hydrogen atom attached to the carbon atom adjacent to the carbonyl group (\(-CHO\)).
The reaction involves disproportionation (self-oxidation and reduction) of the aldehyde in the presence of a concentrated strong base (like NaOH or KOH) to yield a primary alcohol and a salt of a carboxylic acid.
Step 3: Detailed Explanation:
Let's analyze each option based on the conditions for the Cannizzaro reaction.
(A) \( \mathrm{CH_3CHO} \) (Acetaldehyde):
This is an aldehyde. The carbon atom adjacent to the \(-CHO\) group (the \( \alpha \)-carbon) is \( \mathrm{CH_3} \), which has three \( \alpha \)-hydrogens. Therefore, it undergoes Aldol condensation, not the Cannizzaro reaction.
(B) \( \mathrm{C_6H_5CHO} \) (Benzaldehyde):
This is an aldehyde. The \(-CHO\) group is attached to a carbon atom of the benzene ring. This ring carbon is the \( \alpha \)-carbon, and it has no hydrogen atoms attached to it (it is bonded to two other ring carbons and the carbonyl carbon). Since it lacks an \( \alpha \)-hydrogen, it undergoes the Cannizzaro reaction.
\[ 2\mathrm{C_6H_5CHO} + \text{conc. } \mathrm{NaOH} \rightarrow \mathrm{C_6H_5CH_2OH} + \mathrm{C_6H_5COONa} \]
(C) \( \mathrm{CH_3COCH_3} \) (Acetone):
This is a ketone, not an aldehyde. Ketones do not undergo the Cannizzaro reaction.
(D) \( \mathrm{CH_3CH_2OH} \) (Ethanol):
This is an alcohol, not an aldehyde. Alcohols do not undergo the Cannizzaro reaction.
Step 4: Final Answer:
Only Benzaldehyde (\( \mathrm{C_6H_5CHO} \)) satisfies the conditions for the Cannizzaro reaction.