Which of the following reactions involve carbanion enolalte as reactive intermediate?

Options

A. Kolbe-Schmidt reaction
B. Reimer-Tiemann reaction
C. Claisen condensation
D. Aldol condensation

Answer

To determine which of the given reactions involve carbanion enolate as a reactive intermediate, we need to analyze each reaction mentioned: Colway-Semite reaction, Remer-Tiemann reaction, Clayson condensation, and Eldall condensation.

### Step-by-Step Solution:

1. **Understanding Enolate Ion**:
- An enolate ion is formed from a carbonyl compound (like aldehydes or ketones) when a base abstracts a proton from the alpha carbon. This results in a negatively charged carbon (carbanion) adjacent to a carbonyl group.
- For example, from acetone (CH3C(=O)CH3), the enolate ion can be represented as CH3C(=O)CH2^-.

2. **Analyzing Each Reaction**:
- **Colway-Semite Reaction**: This reaction involves the carboxylation of a carbonyl compound. It does not involve enolate ions as intermediates. Instead, it uses CO2 as an electrophile.
- **Remer-Tiemann Reaction**: This reaction involves the formation of a carbene intermediate (specifically dichlorocarbene) and does not utilize enolate ions.
- **Clayson Condensation**: This reaction involves the formation of an enolate ion from a carbonyl compound, which then reacts with another carbonyl compound to form a β-keto ester. Thus, it does involve an enolate intermediate.
- **Eldall Condensation**: Similar to Clayson condensation, this reaction also involves the formation of an enolate ion which acts as a nucleophile in the reaction.

3. **Conclusion**:
- The reactions that involve carbanion enolate as a reactive intermediate are **Clayson Condensation** and **Eldall Condensation**.

### Final Answer:
The reactions that involve carbanion enolate as a reactive intermediate are **Clayson Condensation** and **Eldall Condensation**.

---