Peroxidation in Relation to Olefinic Structure

Abstract

Abstract The process of autoxidation among olefinic substances comprises two major phenomena, that of the incorporation of molecules of oxygen (peroxidation), and that of secondary change (peroxide breakdown) during which the peroxide groups formed by this incorporation act as oxidizing agents for adjacent unsaturated centers. Interest may, accordingly, be directed towards two quite distinct but composite themes, viz. : (1) the nature of the mechanism by which the oxygen molecules are incorporated, the positions they take up in different kinds of organic molecules, and the effect of their introduction in causing (or not causing) specific types of molecule-linking, and (2) the inherent stability or instability of the peroxide groups in different molecules and its structural cause, the mechanism of breakdown of the peroxidic groups and the way this is influenced by light, heat, or catalytic influences, and finally the manner of utilization of the “active” oxygen given up by the decomposing peroxide groups in forming (by inter- or intramolecular reaction) new oxygeno-groups or, alternatively, in bringing about some small or large degree of scission of the carbon chains. Wherever the peroxido-olefins have a moderately high degree of stability, and they are consequently isolable in tolerably pure condition, no serious difficulty attends the systematic study of their thermal, photo-, or catalyzed decomposition, although as yet but little systematic work has been done in this field : but where their degree of unstability is very high, deductions concerning the character of the peroxido-olefinic structures produced and of their breakdown mechanisms have to be made (at any rate in the first place) from the nature of the secondary autoxidation products actually isolated in practice, and there is then grave danger of erroneous conclusions being drawn. Of course, many autoxidation products are extremely complex in character, and where this is the case the difficulty of correlating breakdown products with their peroxidic precursors is greatly increased. Therefore in prosecuting autoxidation studies, especially those directed towards determining the mechanism of reaction, it is very desirable to have as general guide a detailed knowledge of the structure and breakdown behavior of all the various distinctive types of organic peroxide which are capable of existence, and the following survey represents in the main a contribution in this direction.