Question

Ethyl alcohol can be prepared from Grignard reagent by the reaction of:

• A. \( \text{HCHO} \)
• B. \( \text{R}_2\text{CO} \)
• C. \( \text{RCN} \)
• D. \( \text{RCOCl} \)

Hint:

Grignard reagents react with formaldehyde to yield primary alcohols. Other carbonyl compounds typically form secondary or tertiary alcohols depending on the type of carbonyl group.

Answer 1

The Correct Option is A

Grignard reagents are highly reactive and undergo reaction with carbonyl compounds, producing alcohols. The reaction of formaldehyde (\( \text{HCHO} \)) with a Grignard reagent, such as methylmagnesium bromide (\( \text{CH}_3\text{MgBr} \)), results in the formation of a primary alcohol. Reaction mechanism: Step 1: Nucleophilic addition.The methyl group (\( \text{CH}_3 \)), acting as a nucleophile from the Grignard reagent, attacks the electrophilic carbonyl carbon of formaldehyde:\[\text{HCHO} + \text{CH}_3\text{MgBr} \to \text{CH}_3\text{CH}_2\text{OMgBr}.\]Step 2: Hydrolysis.The resultant intermediate alcoholate ion (\( \text{CH}_3\text{CH}_2\text{OMgBr} \)) is hydrolyzed with water, yielding the primary alcohol, ethyl alcohol:\[\text{CH}_3\text{CH}_2\text{OMgBr} + \text{H}_3\text{O}^+ \to \text{CH}_3\text{CH}_2\text{OH}.\] Final Answer:\[\boxed{\text{HCHO}}\]