Explain why polymerisation of accrylonitrile is preferred under ationic polymerisation ,wheereas polymersation of vinylic monomers containing polymersation of vinylic monomers continingEDG is preferred under cation mechanism. (b) Explain the polumerisation of buta-1,3-diene using different routes.

Explain why polymerisation of accrylonitrile is preferred under ationi

1.	Explain why polymerisation of accrylonitrile is preferred under ationic polymerisation ,wheereas polymersation of vinylic monomers containing polymersation of vinylic monomers continingEDG is preferred under cation mechanism. (b) Explain the polumerisation of buta-1,3-diene using different routes.
Answer» Solution :Acrylonitrile `(CH_(2)=CH=CN)`Contains`EWG(-C-=N)`Group which stabilises the carbanion intermediate ,Moreover ,cabianion INTERMEDIATES are produced in both the chain-initiation and chain-propagation steps,hence POLUMERISATION of acrylonitriles is preferred under anionic conditions. (1)Chain-initiation step: (2)Chain propagation step: (ii)Cationic polumerisationof vinylic monomer CONTAINING`EDG`cationic polymerisation is carried out in hte presence of acids.It forms carbocation intermediate and is stabilised by`EDG`both in chain-initiation and in chain -propagation steps.Hence polymersation is preferred under cations conditions. (1)Chain-initiation step: (2)Chain-propagation step: (b)Buta`-1,3-`diene is a conjugate diene which can be polymersation either by `1,4,-`addition or by`1,2-`addition MECHANISM. (i).`1,4-`Polymersation :It gives unbranced polymer. (ii)1,2-Polymersation:it gives branced polymer.