Ethanal and propanone undergo condensation reaction in presence of dil. Alkali to form

Options

A. `CH_3CH(OH) CH_2COCH_3`
B. `CH_3-CO-C(OH)(CH_3)_2`
C. `HOH_2"CCH"_2CH_2COCH_3`
D. `CH_3COCH(CH_3)CH_2OH`

Answer

To solve the problem of what products are formed when ethanal (acetaldehyde) and propanone (acetone) undergo a condensation reaction in the presence of dilute alkali, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants**:
- Ethanal (acetaldehyde) has the formula CH₃CHO.
- Propanone (acetone) has the formula CH₃COCH₃.

2. **Understand the Reaction Medium**:
- The reaction is carried out in a dilute alkaline medium, which typically involves a base like sodium hydroxide (NaOH). This creates a basic environment conducive for condensation reactions.

3. **Formation of Enolate Ion**:
- In the presence of a base, the alpha hydrogen (the hydrogen atom attached to the carbon adjacent to the carbonyl group) of propanone can be deprotonated to form an enolate ion.
- The enolate ion from propanone can be represented as:
\[ CH_3C(O^-)CH_3 \]

4. **Nucleophilic Attack**:
- The enolate ion acts as a nucleophile and can attack the carbonyl carbon of ethanal. This results in the formation of a tetrahedral intermediate.

5. **Formation of the Product**:
- The tetrahedral intermediate will rearrange, leading to the formation of a β-hydroxy ketone (an aldol product). The reaction can be summarized as follows:
\[ CH_3COCH_3 + CH_3CHO \rightarrow CH_3C(OH)(CH_3)CH_2CHO \]
- This product is 4-hydroxy-4-methylpentan-2-one.

6. **Dehydration**:
- Under the reaction conditions, the β-hydroxy ketone can undergo dehydration (loss of water) to form an α,β-unsaturated carbonyl compound:
\[ CH_3C(OH)(CH_3)CH_2CHO \rightarrow CH_3C(CH_3)=CHCHO + H_2O \]

7. **Final Product**:
- The final product of the condensation reaction is 4-methylpent-3-enal (or crotonaldehyde).

### Final Answer:
The condensation reaction of ethanal and propanone in the presence of dilute alkali forms 4-methylpent-3-enal (or crotonaldehyde).