Relative reactivity of cis‐ and trans‐1,3‐pentadiene in the cationic copolymerization with isobutene

Abstract

Abstractcis‐1,3‐Pentadiene (2) and trans‐1,3‐pentadiene (3) were copolymerized with isobutene (1) in the presence of (C2H5)2AlCl+(CH3)3CCl or (C2H5)2AlCl+Cl2 in the range of temperatures between —35 and —70°C. The reactivity ratios, determined at —55°C, are:r1.2=5,0 and r1.3=2,3, while the chain transfer coefficients are Kt.2=50 and Kt.3=113. The activation energies are: EMv.2= —13,8kJ/mol (—3,3 kcal/mol) and EMv.3= —16,7kJ/mol(—4,0 kcal/mol). Spectroscopic analyses (IR, 1H‐NMR) showed that in both copolymers the 1,4‐trans structure is prevalent over the 1,2‐trans‐enchainment. The fact that 3 is more reactive than 2 can be correlated with a greater electron‐density (13C‐NMR data) on C‐1 in compound 3.