Analytical Methods in Rubber Chemistry. Part V. Estimation of the Oxygen of Highly Autoöxidized Rubber Contained in Carboxyl, Ester, Carbonyl, Epoxide and Hydroxyl Groups

Abstract

Abstract In the course of a study of the autoöxidation of natural rubber and of low-molecular olefins of allied structure, it has been necessary to ascertain the nature and relative proportions of the functional groups to which the ingoing oxygen may give rise. Up to the present it has been established that the products of autoöxidation reactions are in general highly complex mixtures, and that even such simple olefins as dihydromyrcene and cyclohexene may give rise to molecules which bear a varied assortment of hydroperoxide, alcoholic hydroxyl, epoxide and carbonyl groups. Available evidence further indicates that the primary products of autoöxidation are hydroperoxides, formed by the reaction of oxygen at methylene groups adjacent to double bonds, and that it is the secondary reactions which these hydroperoxides undergo which are responsible, directly or indirectly, for the formation of the other oxygen-containing groups which have been observed. Molecules of rubber hydrocarbon contain, on an average, several thousand methylene groups adjacent to double bonds. Each such methylene group is at least the potential seat of oxidative attack, and it might be anticipated that if the autoöxidation of rubber proceeds in a manner analogous to that of simpler olefins, the products of reaction would be extremely complex and that they might contain any or all of the following functional groups