A chemical means of distinguishing between conjugated and conjugated bonds

Abstract

AbstractPolymers which contain conjugated bonds (polyenes) cannot be distinguished from polymers containing conjugated bonds (polyimines) by spectral means alone. A chemical means has been found for distinguishing between polyenes and polyimines. Polyenes can be hydrogenated with the aid of palladium supported on charcoal, whereas polymines cannot. On the other hand, polymines can be oxidized by basic hydrogen peroxide, whereas polyenes cannot. Models used for polyene systems were dehydrochlorinated poly(vinyl chloride) and β‐carotene. A model for the polyimine system was polysuccinonitrile. This polymer will pick up oxygen rapidly to form an imine‐nitrone random copolymer. Since discolored polyacrylonitrile, whether discolored by heat or by base, has a reactivity similar to the imine‐nitrone system, it is concluded that the species responsible for color in polyacrylonitrile consists of a conjugated system and not of a conjugated system.