The Course of Autoöxidation Reactions in Polyisoprenes and Allied Compounds. Part. VI. The Peroxidation of Rubber

Peroxides have repeatedly been shown to appear during the slow oxidation (perishing) of rubber in air, and during both its milling in air and the passage of air or oxygen through its solutions: yet in none of the recorded experiments has the production of any very substantial proportion of peroxide been demonstrated. This arises largely because, under many conditions of autoöxidation, no very considerable proportion of peroxide is present in the oxidation product at any stage, but in part because no convenient and reasonably accurate method of determining the peroxide content in so insoluble a substance as rubber has been available. It must inevitably happen in a long-chain molecule of polymer-homologous type containing on the average about 5,000 autoxidisable olefinic units that the progressive entrance of a heterogeneous element will yield a large variety of closely similar products if attack is fairly evenly distributed over the chain, but when, as in the case of oxygen, the heterogeneous element enters the hydrocarbon as a diatomic molecule, the atoms in which can ultimately separate and become attached to the carbon chain in a variety of ways, and causes, as the result of its progressive incorporation, scission of the chain at an ever-increasing number of the olefinic units, then the potential range of diversity of the products becomes enormously increased.