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 can react with carbonyl compounds to form alcohols. When formaldehyde (\( \text{HCHO} \)) reacts with a Grignard reagent like methylmagnesium bromide (\( \text{CH}_3\text{MgBr} \)), a primary alcohol is formed. Reaction mechanism: Step 1: Nucleophilic attack. The nucleophilic methyl group (\( \text{CH}_3 \)) 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 intermediate alcoholate ion (\( \text{CH}_3\text{CH}_2\text{OMgBr} \)) is then hydrolyzed in the presence of water to yield 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: \[ \boxed{\text{HCHO}} \]