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.
MHT CET
Chemistry
Aldehydes and Ketones
2026
MHT CET 2026 (18 April Shift 1)
MHT CET Chemistry Question (2026) — Solution
Options
- A. C _6 H _5 MgCl
- B. C _2 H _5 MgBr
- C. C _6 H _5 MgI
- D. C _6 H _5 MgBr
Answer
D. C _6 H _5 MgBr
Step-by-step solution
Benzonitrile ( C _6 H _5 CN ) reacts with a Grignard reagent to form an imine salt, which on hydrolysis gives a ketone. Since the product is benzophenone ( C _6 H _5 COC _6 H _5), the Grignard reagent must provide a phenyl group ( C _6 H _5^-). The formation of hydroxymagnesium bromide ( Mg(OH)Br ) as a by-product indicates that the halogen in the Grignard reagent is bromine. The reaction is: C _6 H _5 CN + C _6 H _5 MgBr dry ether ( C _6 H _5)_2 C=NMgBr ( C _6 H _5)_2 C=NMgBr + 2 H _2 O ( C _6 H _5)_2 C=O + NH _3 + Mg(OH)Br The reagent used is C _6 H _5 MgBr .
Related: Chemistry — Aldehydes and Ketones · All PYQ Banks