Reaction kinetics of polymer substituents. Neighbouring-substituent effects in single-substituent reactions

Abstract

The kinetic behaviour is predicted for a hypothetical polymer reaction in which the reactivity of a substituent (or other reacting entity) depends on whether zero, one or two of its neighbours have already reacted. The problem is not new, but the method of analysis used here gives solutions applicable to reactions of polymer molecules containing a finite number m, as well as an infinite number (m→∞), of substituents. Results are given showing the variety of plots that can be expected for the extent ξ and the rate [graphic omitted] of reaction, and for the number N_x of sequences of x unreacted substituents. Depending on the relative probabilities of reaction, the overall reaction kinetics can show co-operative (autocatalytic), autoretarding (antico-operative) or random behaviour. Random reaction involving single substituents gives overall first-order kinetics. The mathematical treatment belongs to a class of kinetics and statistics of occupation of a one-dimensional array: the terminology is easily changed from reaction to occupation kinetics.