Which of the following cannot give Cannizzaro reaction?

Options

A.
B.
C. `Cl-underset(Cl)underset(|)overset(Cl)overset(|)C- overset(O)overset(||)C-H`
D. `H-overset(O)overset(||)C-H`

Answer

To determine which of the given compounds cannot undergo the Cannizzaro reaction, we first need to understand the conditions under which this reaction occurs.

### Step-by-Step Solution:

1. **Understanding Cannizzaro Reaction**:
The Cannizzaro reaction involves aldehydes that do not have any alpha-hydrogens. In this reaction, one molecule of the aldehyde is oxidized to a carboxylic acid while another molecule is reduced to an alcohol.

2. **Identifying Aldehydes**:
We need to examine the given options to identify which aldehyde lacks alpha-hydrogens. Aldehydes that cannot undergo Cannizzaro reaction are those that have alpha-hydrogens or can undergo other reactions instead.

3. **Analyzing Each Option**:
- **Option 1: Benzaldehyde (C6H5CHO)**:
- Benzaldehyde has no alpha-hydrogens. Therefore, it can undergo Cannizzaro reaction.
- **Option 2: Acetaldehyde (CH3CHO)**:
- Acetaldehyde has alpha-hydrogens (the methyl group), hence it cannot undergo Cannizzaro reaction.
- **Option 3: Chloral (CCl3CHO)**:
- Chloral does not have alpha-hydrogens, but it can undergo a different reaction (haloform reaction) due to the presence of the CCl3 group. Therefore, it cannot give Cannizzaro products.
- **Option 4: Formaldehyde (HCHO)**:
- Formaldehyde has no alpha-hydrogens and can undergo Cannizzaro reaction.

4. **Conclusion**:
After analyzing all options, we find that **Option 3 (Chloral)** cannot give Cannizzaro reaction because it undergoes a haloform reaction instead.

### Final Answer:
**Chloral (CCl3CHO) cannot give Cannizzaro reaction.**

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