Application of tracer techniques to studies on autoxidation reactions

Abstract

SummaryThe tracers containing deuterium, carbon isotopes, and heavy oxygen that may be applied to the studies on autoxidation reactions are described. The autoxidation of the deuterated compounds formed by replacing hydrogen atoms on the double bond has given concrete experimental evidence for the following phenomena of autoxidation reaction: a) initial attack of oxygen at the double bond and the inherent induction period, b) the propagation of autoxidation by attack on the methylenic group, alpha to the double bond during the steady state, c) the presence of resonance in the free radicals formed and consequent shifting of the double bond, and d) the location of the hydrogen atoms contributing to the formation of the major portion of the water.These investigations have led to the elucidation of some aspects of the mechanism of decomposition of peroxides and consequent formation of hydroxyl radicals, which attack the substrates at certain preferential points giving rise to water. They also provide the mechanisms of cleavage and formation of the volatile products.Our experiments have also established four different and distinct stages of autoxidation. Water formation in autoxidation is shown to be the outcome of the primary decomposition of peroxides, mainly hydroperoxides, and the formation of the organic volatile products to be that of the secondary decomposition at a later stage. These processes have been correlated to the bond strengths of the different atoms in the substrates and the resulting products. The advantages and disadvantages of the application of these tracer techniques to autoxidation reactions in general are also discussed.