Question

Identify the product ' B ' in following reaction.
\(\text{Dry ice} \xrightarrow[\text{dry ether}]{\text{CH}_3\text{MgBr}} \text{A} \xrightarrow{\text{H}_3\text{O}^+} \text{B}\)

• A. Methanoic acid
• B. Ethanoic acid
• C. Methanol
• D. Ethanol

Hint:

Grignard reagent + \(\text{CO}_2\) + hydrolysis gives a carboxylic acid with one extra carbon atom.

Answer 1

The Correct Option is B

Concept:
Grignard reagents react with carbon dioxide to form magnesium salts of carboxylic acids, which on acidic hydrolysis give carboxylic acids. ip

Step 1: Identify dry ice.
Dry ice is solid carbon dioxide: \[ \text{CO}_2 \] ip

Step 2: React \(\text{CH}_3\text{MgBr}\) with \(\text{CO}_2\).
Methyl magnesium bromide reacts with carbon dioxide to give the magnesium salt of acetic acid. Intermediate \(A\) is: \[ \text{CH}_3\text{COOMgBr} \] ip

Step 3: Hydrolyse the intermediate.
On treatment with \(\text{H}_3\text{O}^+\), the magnesium salt gives: \[ \text{CH}_3\text{COOH} \] which is ethanoic acid. ip Hence, the correct answer is:
\[ \boxed{(B)\ \text{Ethanoic acid}} \]