Question

Explain why cationic polymerization is an effective method of polymerizing ${\mathbf{CH}}_{\mathbf{2}}\mathbf{=}\mathbf{C}{\left({\mathrm{CH}}_3\right)}_{\mathbf{2}}$ but not${\mathbf{CH}}_{\mathbf{2}}\mathbf{=}{\mathbf{CH}}_{\mathbf{2}}$ .

Short answer

Answer

More stable 3° carbocations readily react in cationic polymerization than the 1° carbocations. Among two , ${\mathrm{CH}}_2=\mathrm{C}{\left({\mathrm{CH}}_2\right)}_3$will form a more substituted carbocation than${\mathrm{CH}}_2={\mathrm{CH}}_2$ .

Step-by-step solution

Cationic polymerization

The polymerization technique, in which there will be a cationic initiator that transfers charge to the monomer to become reactive. The reactive monomers get added in a similar way to form polymers.

Reason why cationic polymerization is effective for the first compound

The phenomenon of cationic polymerization proceeds via a carbocation intermediate. The substrate that forms stable 3° carbocations have more capability to react. But 1° carbocations is less stable.

Thus, ${\mathrm{CH}}_2=\mathrm{C}{\left({\mathrm{CH}}_3\right)}_2$will form a more substituted carbocation than${\mathrm{CH}}_2={\mathrm{CH}}_2$ .

Diagrammatic representation

Formation of more substituted carbocation