The compound shown is a monomer. Among the structures shown (short fragments of polymer chains, end groups drawn), which one is a fragment of the polymer obtained from this monomer, and is therefore the only one that can be crosslinked by heating with sulfur?

AStructure A
BStructure B
CStructure C
DStructure D

Answer: C

The monomer shown is isoprene (2-methylbuta-1,3-diene); its 1,4-addition polymer is polyisoprene (natural rubber), structure C, which retains one C=C per repeat unit. Sulfur vulcanisation needs C=C bonds with allylic hydrogens. Polystyrene, poly(vinyl chloride) and polyethylene (structures A, B, D) have saturated backbones, so sulfur cannot link their chains.

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The compound shown is a monomer. Among the structures shown (short fragments of polymer chains, end groups drawn), which one is a fragment of the polymer obtained from this monomer, and is therefore the only one that can be crosslinked by heating with sulfur?

Answer: C

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