Which among the following is used as a monomer for the preparation of neoprene?

Which of the following polymerisation reactions leads to the formation of neoprene?

The catalyst used for olefin polymerization is

In the production of thermosetting polymers,which substance is used along with methanal?

The major product of the following reaction is:

The Ziegler-Natta catalyst used for polymerisation of ethene and styrene is $TiCl_4 + (C_2H_5)_3Al$. The catalysing species (active species) involved in the polymerisation is