Organic Chemistry Multiple Choice Questions on “Free Radical Vinyl Polymerisation”.
1. Which of the following is an initiator molecule in the free radical polymerisation?
a) Benzoyl peroxide
b) Sulphuric acid
c) Potassium permanganate
d) Chromium oxide
Answer: a
Clarification: The whole process of free radical polymerisation starts off with a molecule called an initiator. This is a molecule like benzoyl peroxide. When they split, the pair of electrons in the bond which is broken will separate. This is unusual as electrons like to be in pairs whenever possible. When this split happens, we’re left with two fragments, called initiator fragments.
2. Why is vinyl polymerization also known as addition polymerization?
a) monomers are unsaturated compounds
b) it is a chain reaction
c) most monomers contain (CH2=CH─) group
d) it proceeds through radical
Answer: c
Clarification: In addition polymerisation, polymer are formed by simple linking of monomers without the co-generation of other products. Most of the monomers involves in chain polymerization contains (CH2=CH─) group, known as vinyl group.
3. Which of the following happens in initiation step of the free radical polymerisation?
a) Decomposition of initiator
b) Renewal of inhibitor
c) Addition of monomer molecules to the growing chains
d) Disproportionation
Answer: a
Clarification: The breakdown of the initiator molecule to form radicals, followed by the radical’s reaction with a monomer molecule is called the initiation step of the polymerization.
4. Which of the following happens in propagation step of the free radical polymerisation?
a) Decomposition of initiator
b) Renewal of inhibitor
c) Addition of monomer molecules to the growing chains
d) Disproportionation
Answer: b
Clarification: The adding of more and more monomer molecules to the growing chains, is called propagation. Self-perpetuating reactions like this one are called chain reactions.
5. Which of the following happens in termination step of the free radical polymerisation?
a) decomposition of initiator
b) addition of free radical to monomer
c) addition of monomer molecules to the growing chains
d) disproportionation
Answer: d
Clarification: Termination reaction in which our unpaired electrons can shut down the polymerization: it’s is called disproportionation. This is a rather complicated way in which two growing polymer chains solve the problem of their unpaired electrons.
6. Which of the following reagents may be used to initiate radical polymerization of styrene?
a) HCl
b) Peroxides
c) Hydroxide ion
d) BF3
Answer: b
Clarification: The whole process of free radical polymerisation starts off with a molecule called an initiator. This is a molecule like peroxide or AIBN.
7. Which polymer will be formed when vinyl acetate reacts with peroxides?
a) 
b) 
c) 
d) 
Answer: a
Clarification: Polyvinyl acetate, or PVA for short, is one of those low-profile behind-the-scenes polymers. It is found in the case with polyethylene or polystyrene.
