Cannizzaro reaction is not given by

Options

A. trimethylacetaldehyde
B. acetaldehyde
C. benzaldehyde
D. formaldehyde.

Explanation

To determine which compound does not undergo the Cannizzaro reaction, we need to understand the conditions under which this reaction occurs. The Cannizzaro reaction is a redox reaction that typically takes place with aldehydes that lack alpha-hydrogens.

### Step-by-Step Solution:

1. **Identify the Cannizzaro Reaction**:
The Cannizzaro reaction involves the disproportionation of non-enolizable aldehydes (those without alpha-hydrogens) in the presence of a strong base, leading to the formation of an alcohol and a carboxylic acid.

2. **Understand Alpha-Hydrogens**:
Alpha-hydrogens are the hydrogen atoms attached to the carbon adjacent to the carbonyl group (C=O). If an aldehyde has alpha-hydrogens, it can undergo aldol condensation instead of the Cannizzaro reaction.

3. **Analyze the Given Compounds**:
- **Trimethylacetaldehyde**: This compound has the structure (CH3)3CCHO. It has no alpha-hydrogens because the carbon adjacent to the carbonyl group is bonded to three methyl groups. Therefore, it can undergo the Cannizzaro reaction.
- **Acetaldehyde (CH3CHO)**: This compound has alpha-hydrogens (the hydrogen on the carbon adjacent to the carbonyl). Thus, it cannot undergo the Cannizzaro reaction but can undergo aldol condensation.
- **Benzaldehyde (C6H5CHO)**: This compound also has no alpha-hydrogens, as the carbon adjacent to the carbonyl is part of a phenyl group. Therefore, it can undergo the Cannizzaro reaction.
- **Formaldehyde (HCHO)**: This compound has no alpha-hydrogens and can also undergo the Cannizzaro reaction.

4. **Conclusion**:
Among the given options, acetaldehyde is the only compound that has alpha-hydrogens and therefore cannot undergo the Cannizzaro reaction.

### Final Answer:
**Acetaldehyde does not undergo the Cannizzaro reaction.**