Which compounds do not undergo Cannizzaro Reaction ?

Options

A. methanal
B. Tricholoroacetaldyde
C. Benzaldehyde
D. Ethanal

Answer

To determine which compounds do not undergo the Cannizzaro Reaction, we need to understand the requirements for a compound to participate in this reaction. The Cannizzaro Reaction typically occurs with aldehydes that do not have any alpha hydrogen atoms. Here’s a step-by-step solution to the question:

### Step 1: Understand the Cannizzaro Reaction
The Cannizzaro Reaction is a redox reaction where non-enolizable aldehydes (those without alpha hydrogen) undergo disproportionation in the presence of a strong base, leading to the formation of an alcohol and a carboxylic acid.

### Step 2: Identify the Criteria for Cannizzaro Reaction
For a compound to undergo the Cannizzaro Reaction, it must:
- Be an aldehyde (or certain ketones).
- Have no alpha hydrogen atoms.

### Step 3: Analyze the Given Options
Let’s analyze each option provided in the question to see if they meet the criteria.

#### Option A: Methanol (CH3OH)
- Methanol is an alcohol, not an aldehyde, so it does not undergo the Cannizzaro Reaction.

#### Option B: Trichloroacetaldehyde (CCl3CHO)
- This compound has no alpha hydrogen atoms (the carbon adjacent to the carbonyl carbon has three chlorine atoms instead). Therefore, it can undergo the Cannizzaro Reaction.

#### Option C: Benzaldehyde (C6H5CHO)
- Benzaldehyde also has no alpha hydrogen atoms (the carbon adjacent to the carbonyl carbon is part of the benzene ring). Thus, it can undergo the Cannizzaro Reaction.

#### Option D: Ethanol (C2H5OH)
- Ethanol is an alcohol and does not have a carbonyl group, so it cannot undergo the Cannizzaro Reaction.

### Step 4: Conclusion
Based on the analysis:
- **Compounds that do not undergo the Cannizzaro Reaction:** Methanol (A) and Ethanol (D).
- **Compounds that can undergo the Cannizzaro Reaction:** Trichloroacetaldehyde (B) and Benzaldehyde (C).

### Final Answer
The compounds that do not undergo the Cannizzaro Reaction are **Methanol (A)** and **Ethanol (D)**.