Question

Which of the following compound gives only primary alcohol on reaction with Grignard Reagent (RMgX)?

• A. \(\mathrm{CH_3CH_2CHO}\)
• B. \(\mathrm{HCHO}\)
• C. \(\mathrm{CH_3CH_2COCH_3}\)
• D. \(\mathrm{C_2H_5COCH_3}\)

Hint:

Shortcut yaad rakho: HCHO → 1° alcohol, aldehyde → 2°, ketone → 3° alcohol.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Grignard reagents react with carbonyl compounds to form alcohols. The degree of the alcohol depends on the starting carbonyl.
Step 2: Formula Application:
1. Formaldehyde (HCHO) $\to$ Primary ($1^{\circ}$) alcohol. 2. Other Aldehydes (RCHO) $\to$ Secondary ($2^{\circ}$) alcohol. 3. Ketones (RCOR) $\to$ Tertiary ($3^{\circ}$) alcohol.
Step 3: Explanation:
Formaldehyde ($HCHO$) has two hydrogens attached to the carbonyl carbon. After the Grignard $R$ group adds, the carbon will have two H atoms and one R group, making it a primary alcohol.
Step 4: Final Answer:
Formaldehyde ($HCHO$) produces a primary alcohol.