The reactivities of the oxime groups in 4-vinyl- and 2-methyl-5-vinylpyridine copolymers with their n-phenacyloxime derivatives

Abstract

The acylation kinetics of the oxime group present in poly-4-vinylpyridine and poly-2-methyl-5-vinylpyridine partly quaternized with bromophenacyloxime have been studied. A considerable increase in the nucleophilicity of the oxime groups present in the copolymers has been detected when they were compared with the respective low molecular weight analogues; it was accompanied by an anomalous p K a reduction. We also show that the rate constant for acylation decreases in the copolymers with the quaternization efficiency of the polymer; in contrast with the low molecular weight analogues it also strongly and exclusively depends on the concentration of various low molecular weight salts present in the reaction mixture. All these effects are due to a large extent to the influence of the micro-environment and the electrostatic reaction of the pyridine, having a positive charge with the oxime with its negative charge.