Which of the following does not undergo benzoin condensation?

Options

A. benzene carbaldehyde
B. p toulene carbaldehyde
C. phenylethanal
D. 4-methooxy benzaldehyde

Answer

To determine which of the following compounds does not undergo benzoin condensation, we first need to understand the conditions necessary for this reaction. Benzoin condensation specifically requires aromatic aldehydes, where the aldehyde group (CHO) is directly attached to an aromatic ring.

### Step-by-Step Solution:

1. **Understanding Benzoin Condensation**:
- Benzoin condensation is a reaction that occurs between two aromatic aldehydes in the presence of a cyanide ion (CN-) to form benzoin, which contains two benzene rings, one hydroxyl group (OH), and one carbonyl group (C=O).

2. **Identifying the Required Structure**:
- For a compound to undergo benzoin condensation, it must be an aromatic aldehyde. This means the aldehyde group must be directly attached to the benzene ring.

3. **Analyzing the Given Options**:
- **Option 1: Benzene carbaldehyde (Benzaldehyde)**: This is an aromatic aldehyde and can undergo benzoin condensation.
- **Option 2: Para-toluene carbaldehyde**: This is also an aromatic aldehyde (toluene with a CHO group at the para position) and can undergo benzoin condensation.
- **Option 3: Phenyl ethanol**: This compound has an alcohol group (OH) attached to a carbon chain, and the aldehyde group is not directly attached to the aromatic ring. Therefore, it is classified as an aliphatic aldehyde and does not undergo benzoin condensation.
- **Option 4: 4-methoxybenzaldehyde**: This is an aromatic aldehyde (the aldehyde group is directly attached to the benzene ring) and can undergo benzoin condensation.

4. **Conclusion**:
- The compound that does not undergo benzoin condensation is **Phenyl ethanol** (Option 3), as it does not meet the requirement of having the aldehyde group directly attached to the aromatic ring.

### Final Answer:
**Phenyl ethanol does not undergo benzoin condensation.**