Isomeric active ends of growing chains in the cationic polymerization of 4-methyl-1-pentene

Quantum chemical investigation of the relative stabilities of carbenium ions modelling the end units of growing chains in the cationic polymerization of 4-methyl-1-pentene has been carried out. The investigation was performed by the CNDO/2 method and by partial optimization of geometry. It is shown that the polymer chain can be adequately modelled by a methyl group. The calculated values of relative energies ΔE, geometric parameters and charge distribution are given for free cations, ion-pairs and for the cation-electron donor and cation-electron acceptor systems (H₂O, HCN and NO₂). All the additives show donor behaviour with respect to cations. The differences in the energies of secondary and tertiary cations decrease on going from free ions to ion-pairs or cation-additive molecule system.