Question

............... act as a catalyst in anionic polymerisation.

• A. Grignard reagent
• B. Lewis acids
• C. Benzoyl peroxide
• D. AIBN

Hint:

Anionic polymerisation requires nucleophilic initiators like Grignard reagents. Radical initiators like AIBN are for free radical processes.

Answer 1

The Correct Option is A

Anionic polymerisation is a type of chain-growth polymerisation that is initiated by a nucleophile — a species that donates an electron pair. It typically involves monomers that have electron-withdrawing groups, such as styrene, acrylonitrile, or butadiene.
To initiate such polymerisation, the catalyst must be capable of generating a negatively charged active center.
- Grignard reagents (RMgX) contain a highly polar carbon-magnesium bond. The carbon bonded to Mg acts as a strong nucleophile. This makes Grignard reagents suitable for initiating anionic polymerisation reactions by donating an electron pair to the monomer.
- Lewis acids are electron pair acceptors and are instead used in cationic polymerisation, not anionic.
- Benzoyl peroxide and AIBN (Azobisisobutyronitrile) are radical initiators, typically used in free radical polymerisation, not in ionic polymerisation mechanisms.
Therefore, the Grignard reagent is the correct catalyst for anionic polymerisation.