The intermediate formed in aldol condensation is

Options

A. aldol
B. carbanion
C. alcohol
D. ` alpha`-hydrogen ester .

Explanation

To solve the question regarding the intermediate formed in aldol condensation, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding Aldol Condensation**:
Aldol condensation is a reaction between carbonyl compounds that contain alpha hydrogen atoms. It involves the formation of a β-hydroxy carbonyl compound (aldol) and subsequently dehydration to form an α,β-unsaturated carbonyl compound.

2. **Formation of Carbanion**:
When a carbonyl compound (like acetaldehyde, CH3CHO) is treated with a base (like OH⁻), the base abstracts an alpha hydrogen from the carbon adjacent to the carbonyl group. This leads to the formation of a carbanion, which is a negatively charged carbon species.

3. **Example with Acetaldehyde**:
In our example, when acetaldehyde is treated with OH⁻, the base abstracts an alpha hydrogen from the acetaldehyde, forming a carbanion (CH2=CHO⁻). This carbanion acts as a nucleophile.

4. **Nucleophilic Attack**:
The carbanion then attacks another molecule of acetaldehyde at the carbonyl carbon. This results in the formation of a β-hydroxy aldehyde (aldol), which is CH3-CHOH-CH2CHO.

5. **Final Product Formation**:
The aldol can then undergo dehydration (loss of water) to form an α,β-unsaturated carbonyl compound. However, the question specifically asks for the intermediate formed during the aldol condensation.

6. **Identifying the Intermediate**:
The intermediate formed during the aldol condensation is the carbanion, as it is the species formed after the base abstracts the alpha hydrogen.

7. **Conclusion**:
Therefore, the correct answer to the question regarding the intermediate formed in aldol condensation is **carbanion**.

### Final Answer:
The intermediate formed in aldol condensation is **carbanion**.

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