The self condensation of aromatic aldehydes with no $\alpha$-hydrogen in presence of cyanide ion as catalyst to $\alpha$-hydroxy ketone is called :

Question

Accepted Answer

The self-condensation of aromatic aldehydes with no $\alpha$-hydrogen in the presence of a cyanide ion as a catalyst to form $\alpha$-hydroxy ketone is known as Benzoin condensation. Let's explore why Option 2 is the correct answer and why the other options are incorrect.

1. **Benzoin Condensation (Option 2):** 
   - Benzoin condensation is a reaction that involves the coupling of two molecules of an aromatic aldehyde, such as benzaldehyde, in the presence of a cyanide ion catalyst. This reaction results in the formation of an $\alpha$-hydroxy ketone, specifically benzoin. The cyanide ion acts as a nucleophile, attacking the carbonyl carbon of the aldehyde, which leads to the formation of a cyanohydrin intermediate. This intermediate then undergoes further reaction to yield the final $\alpha$-hydroxy ketone product. This process is characteristic of benzoin condensation, making Option 2 the correct choice.

2. **Canizzaro's Reaction (Option 1):**
   - Canizzaro's reaction involves the disproportionation of non-enolizable aldehydes (aldehydes without $\alpha$-hydrogens) in the presence of a strong base, typically yielding an alcohol and a carboxylic acid salt. This reaction does not involve the formation of $\alpha$-hydroxy ketones, and it does not use cyanide ions as a catalyst. Therefore, Option 1 is incorrect in the context of the given reaction.

3. **Perkin Condensation (Option 3):**
   - Perkin condensation is a reaction used to synthesize cinnamic acids by the condensation of an aromatic aldehyde with an anhydride in the presence of a base. This reaction is not related to the formation of $\alpha$-hydroxy ketones and does not involve cyanide ions. Thus, Option 3 is not applicable to the described reaction.

4. **Stobbe Condensation (Option 4):**
   - Stobbe condensation involves the reaction of an aldehyde or ketone with a diester of succinic acid to form a substituted succinic acid derivative. This reaction is distinct from benzoin condensation and does not involve the formation of $\alpha$-hydroxy ketones or the use of cyanide ions. Therefore, Option 4 is incorrect for the given reaction.

In conclusion, the correct answer is Option 2, Benzoin condensation, as it specifically describes the self-condensation of aromatic aldehydes with no $\alpha$-hydrogen in the presence of a cyanide ion catalyst to form $\alpha$-hydroxy ketones.