Question

Benzonitrile on reaction with a reagent in dry ether followed by hydrolysis forms benzophenone along with ammonia and hydroxymagnesium bromide. Identify the reagent used in above transformation.

• A. \(\text{C}_6\text{H}_5\text{MgCl}\)
• B. \(\text{C}_2\text{H}_5\text{MgBr}\)
• C. \(\text{C}_6\text{H}_5\text{MgI}\)
• D. \(\text{C}_6\text{H}_5\text{MgBr}\)

Hint:

The Grignard reagent must supply a phenyl group, and bromide shows in the by-product.

Answer 1

The Correct Option is D

Step 1: Use the by-product clue:
$\text{Mg(OH)Br}$ has bromine, so the Grignard reagent has bromine.

Step 2: Use the product clue:
The ketone has two phenyl groups, so the reagent carries a phenyl group. Only $\text{C}_6\text{H}_5\text{MgBr}$ meets both clues.

Final Answer:
The reagent is $\text{C}_6\text{H}_5\text{MgBr}$, option (D). \[ \boxed{\text{C}_6\text{H}_5\text{MgBr}} \]