The Cannizaro reaction is not given by

Options

A. Trimethyl acetaldehyde
B. Acetaldehyde
C. Benzaldehyde
D. Formaldehyde

Answer

To determine which compound does not undergo the Cannizzaro reaction, we need to understand the conditions required for this reaction to occur. The Cannizzaro reaction is a disproportionation reaction that occurs with aldehydes that lack alpha hydrogens.

### Step-by-Step Solution:

1. **Identify the Cannizzaro Reaction**:
- The Cannizzaro reaction occurs with aldehydes that do not have alpha hydrogens. In this reaction, one molecule of the aldehyde is oxidized to a carboxylic acid while another molecule is reduced to an alcohol in the presence of a strong base.

2. **Analyze the Given Compounds**:
- We need to evaluate each of the four compounds to see if they contain alpha hydrogens or not. The presence of alpha hydrogens will prevent the compound from undergoing the Cannizzaro reaction.

3. **Evaluate Each Compound**:
- **Trimethylacetaldehyde**:
- Structure: (CH3)3CCHO
- Alpha Carbon: The carbon adjacent to the carbonyl (CHO) has no hydrogen atoms (it is bonded to three methyl groups).
- Conclusion: No alpha hydrogens present, so it can undergo Cannizzaro reaction.

- **Acetaldehyde**:
- Structure: CH3CHO
- Alpha Carbon: The carbon adjacent to the carbonyl (CHO) has one hydrogen atom.
- Conclusion: Alpha hydrogen present, so it will not undergo Cannizzaro reaction; it will undergo aldol condensation instead.

- **Benzaldehyde**:
- Structure: C6H5CHO
- Alpha Carbon: The carbon adjacent to the carbonyl (CHO) has no hydrogen atoms (it is bonded to a phenyl group).
- Conclusion: No alpha hydrogens present, so it can undergo Cannizzaro reaction.

- **Formaldehyde**:
- Structure: HCHO
- Alpha Carbon: The carbon adjacent to the carbonyl (CHO) has no hydrogen atoms.
- Conclusion: No alpha hydrogens present, so it can undergo Cannizzaro reaction.

4. **Final Conclusion**:
- The compound that does not undergo the Cannizzaro reaction is **Acetaldehyde** because it has alpha hydrogens.