The reaction is an application of which of the following reaction?

Question

Accepted Answer

The reaction given in the question is:

$$ CH_3COCH_3 + CH_3COCH_3 \xrightarrow[KOH, \Delta]{-H_2O} (CH_3)_2C=CHCOCH_3 $$

This reaction is an application of the Aldol condensation, which is correctly identified as Option 2. Here's why:

### Explanation for Option 2: Aldol Condensation

1. **Definition of Aldol Condensation**: Aldol condensation is a reaction in which an enolate ion reacts with a carbonyl compound to form a β-hydroxy ketone or aldehyde, followed by dehydration to give a conjugated enone.

2. **Mechanism**: In the given reaction, acetone ($CH_3COCH_3$) undergoes deprotonation in the presence of a base (KOH) to form an enolate ion. This enolate ion then attacks another molecule of acetone at the carbonyl carbon, forming a β-hydroxy ketone intermediate. Upon heating ($\Delta$), this intermediate undergoes dehydration (loss of water, $-H_2O$) to form the α,β-unsaturated ketone $(CH_3)_2C=CHCOCH_3$.

3. **Characteristics**: The reaction involves the formation of a carbon-carbon bond and the creation of a double bond through dehydration, which are hallmark features of aldol condensation.

### Explanation for Why Other Options are Incorrect

1. **Option 1: Cannizzaro Reaction**: 
   - The Cannizzaro reaction involves the base-induced disproportionation of non-enolizable aldehydes to yield an alcohol and a carboxylic acid. It does not involve ketones or the formation of carbon-carbon double bonds, making it irrelevant to the given reaction.

2. **Option 3: Hofmann Reaction**:
   - The Hofmann reaction typically refers to the Hofmann rearrangement, where an amide is converted to an amine with one fewer carbon atom. This reaction does not involve ketones or the formation of enones, and thus does not apply to the given reaction.

3. **Option 4: Curtius Reaction**:
   - The Curtius reaction involves the decomposition of an acyl azide to form an isocyanate, which can further react to form amines or other derivatives. This reaction does not involve ketones or the formation of carbon-carbon double bonds, making it unrelated to the reaction in question.

In conclusion, the given reaction is a classic example of aldol condensation, as it involves the formation of a β-hydroxy ketone intermediate and subsequent dehydration to form an α,β-unsaturated ketone. Therefore, Option 2 is the correct answer.