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 following compounds cannot give the Cannizzaro reaction, we need to understand the conditions required for this reaction to occur. The Cannizzaro reaction typically occurs with aldehydes that do not have alpha hydrogens.

### Step-by-Step Solution:

1. **Understanding the Cannizzaro Reaction**:
- The Cannizzaro reaction involves the disproportionation of non-enolizable aldehydes (those without alpha hydrogens) in the presence of a strong base (like NaOH or KOH) to produce an alcohol and a carboxylic acid.

2. **Identifying Aldehydes**:
- We need to analyze the given compounds to check for the presence of alpha hydrogens. Aldehydes that lack alpha hydrogens can undergo the Cannizzaro reaction.

3. **Analyzing Each Compound**:
- **Compound 1: Benzaldehyde (C6H5CHO)**:
- Benzaldehyde has no alpha hydrogens (the carbon adjacent to the carbonyl carbon is part of the aromatic ring). Thus, it can undergo the Cannizzaro reaction.
- **Compound 2: Formaldehyde (HCHO)**:
- Formaldehyde also has no alpha hydrogens. Therefore, it can undergo the Cannizzaro reaction as well.
- **Compound 3: Chloral (CCl3CHO)**:
- Chloral has no alpha hydrogens, but it is an exception. Although it seems like it should undergo the Cannizzaro reaction, it does not because it favors a different reaction (the haloform reaction) due to the presence of the three chlorine atoms, which are good leaving groups.
- **Compound 4: Acetaldehyde (CH3CHO)**:
- Acetaldehyde has alpha hydrogens (the methyl group has hydrogens), so it cannot undergo the Cannizzaro reaction.

4. **Conclusion**:
- Among the compounds analyzed, Chloral is the one that cannot give the Cannizzaro reaction due to its tendency to undergo the haloform reaction instead. Therefore, the answer is **Chloral (CCl3CHO)**.

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