Which of the following alcohols cannot be prepared by the action of a suitable Grignard reagent on an aldehyde or a ketone followed by hydrolysis ?

Options

A. ethyl alcohol
B. isopropyl alcohol
C. n-propyl alcohol
D. methanol

Explanation

To determine which of the following alcohols cannot be prepared by the action of a suitable Grignard reagent on an aldehyde or a ketone followed by hydrolysis, we need to analyze each option:

1. **Understanding Grignard Reagents**: Grignard reagents are of the form R-MgX, where R is an alkyl or aryl group and X is a halogen. When a Grignard reagent reacts with an aldehyde or ketone, it forms an alcohol after hydrolysis.

2. **Alcohols in the Options**:
- Ethyl alcohol (C2H5OH)
- Isopropyl alcohol (C3H8O)
- n-Propyl alcohol (C3H8O)
- Methanol (CH3OH)

3. **Analyzing Each Alcohol**:
- **Ethyl alcohol (C2H5OH)**: This can be prepared by reacting a Grignard reagent like CH3MgBr with formaldehyde (HCHO). The reaction would yield CH3CH2OH after hydrolysis.
- **Isopropyl alcohol (C3H8O)**: This can be prepared by reacting CH3MgBr with acetone (CH3COCH3). The product after hydrolysis would be (CH3)2CHOH.
- **n-Propyl alcohol (C3H8O)**: This can also be prepared by reacting CH3MgBr with propanal (C2H5CHO). The product after hydrolysis would be CH3CH2CH2OH.
- **Methanol (CH3OH)**: Methanol cannot be prepared using Grignard reagents because the smallest aldehyde is formaldehyde (HCHO) and the smallest Grignard reagent is CH3MgX. The reaction of CH3MgX with formaldehyde will yield ethyl alcohol (C2H5OH) and not methanol.

4. **Conclusion**: Therefore, the alcohol that cannot be prepared by the action of a suitable Grignard reagent on an aldehyde or a ketone followed by hydrolysis is **methanol (CH3OH)**.

### Final Answer:
**Methanol (CH3OH)** cannot be prepared by the action of a suitable Grignard reagent on an aldehyde or a ketone followed by hydrolysis.