In which of the following chain termination step is absent?

• A

  Polymerisation of $\mathrm{C}_6 \mathrm{H}_5 \mathrm{CH}=\mathrm{CH}_2$ by $\mathrm{RLi}$
• B

  Polymerisation of $\mathrm{C}_6 \mathrm{H}_5 \mathrm{CH}=\mathrm{CH}_2$ by $\mathrm{BF}_3$ and $\mathrm{H}_2 \mathrm{O}$
• Correct answer
  C

  
  
• D

  Polymerisation of $\mathrm{C}_6 \mathrm{H}_5 \mathrm{CH}=\mathrm{CH}_2$ by $\left(\mathrm{C}_6 \mathrm{H}_5 \mathrm{COO}\right)_2$

Solution

In the polymerisation of $\mathrm{C}_6 \mathrm{H}_5-\mathrm{CH}=\mathrm{CH}_2$ by $\mathrm{RLi}$, free radicals like $\mathrm{C}_6 \mathrm{H}_5-\mathrm{CH}=\underset{\mathrm{R}}{\mathrm{CH}_2}$ and
are formed. These radicals are very stable and thus the chain termination step is less favourable and does not occur.

Hence, the correct answer is option: 'C'.