Which of the following on reaction with conc. NaOH gives an alcohol ?

Options

A. Methanal
B. Ethanal
C. Propanal
D. Butanal

Answer

To solve the question of which of the following compounds reacts with concentrated NaOH to give an alcohol, we will analyze each option based on the conditions of the K-nezaro reaction.

### Step-by-Step Solution:

1. **Understanding the K-nezaro Reaction**:
- The K-nezaro reaction involves the reaction of aldehydes or ketones with concentrated sodium hydroxide (NaOH) in the absence of alpha-hydrogens. This reaction typically leads to the formation of an alcohol and a carboxylic acid.

2. **Identifying the Options**:
- The options given are:
- Methanol
- Ethanol
- Propanol
- Butanol

3. **Analyzing Each Compound**:
- **Methanol (CH₃OH)**: Methanol is not an aldehyde or ketone; it is an alcohol. Therefore, it cannot undergo the K-nezaro reaction.
- **Ethanol (C₂H₅OH)**: Ethanol is also an alcohol and does not have a carbonyl group (C=O) to react with NaOH.
- **Propanol (C₃H₇OH)**: Propanol is another alcohol and similarly lacks a carbonyl group.
- **Butanol (C₄H₉OH)**: Butanol, like the others, is an alcohol and does not have a carbonyl group.

4. **Conclusion**:
- All the given options (Methanol, Ethanol, Propanol, Butanol) are alcohols and do not contain a carbonyl group necessary for the K-nezaro reaction. Therefore, none of these compounds will react with concentrated NaOH to produce an alcohol.

### Final Answer:
None of the given options (Methanol, Ethanol, Propanol, Butanol) react with concentrated NaOH to give an alcohol.