What is the name of monomer used in the formation of a polymer ?

Step-by-step solution

The repeating unit –CH ₂ –C(CH ₃) =CH–CH ₂ – indicates 1,4-addition polymerization of a conjugated diene. Reversing the polymerization by breaking the terminal single bonds and reforming the conjugated system yields the monomer CH ₂ =C(CH ₃) –CH=CH ₂ , known as isoprene. Comparing with options: tetrafluoroethylene ( CF ₂ =CF ₂ ) forms Teflon; acrylonitrile ( CH ₂ =CH–CN ) forms polyacrylonitrile; caprolactam undergoes ring-opening polymerization to form Nylon-6. Only isoprene corresponds to the given structure. Fin