Question

Which of the following Grignard Reagent will be used to prepare cyclohexylmethanol when treated with methanal?

• A. A
• B. B
• C. C
• D. D

Hint:

Grignard + Methanal \(\rightarrow\) \( 1^\circ \) Alcohol.
Grignard + other Aldehydes \(\rightarrow\) \( 2^\circ \) Alcohol.
Grignard + Ketones \(\rightarrow\) \( 3^\circ \) Alcohol.

Answer 1

The Correct Option is B

Step 1: Conceptual Understanding:
When a Grignard reagent (\( R-MgX \)) reacts with methanal (\( HCHO \)), followed by acid hydrolysis, it always produces a primary alcohol with one additional carbon atom. The general reaction leads to the formation of a primary alcohol, \( R-CH_2OH \).
Step 2: Detailed Explanation:
The target product here is cyclohexylmethanol, which has the structure: (Cyclohexyl ring)\( -CH_2OH \).
From the general reaction mechanism, we know that the \( -CH_2OH \) part of the product comes from methanal (\( HCHO \)).
To form this product, the \( R \) group must be the cyclohexyl group, as it is attached to the \( -CH_2OH \) group in the final product. Therefore, the Grignard reagent required must be cyclohexylmagnesium bromide, which will provide the cyclohexyl group.
Step 3: Final Answer:
The correct Grignard reagent required is cyclohexylmagnesium bromide.