Liquid-phase oxidation is discussed in terms of the free radical chain mechanism proposed by BOLLAND and his co-workers. This scheme was devised for certain oxidations in which hydroperoxide is the major product. It is shown, however, that this mechanism is applieable in its essentials to other oxidations in which the hydroperoxide Is not the main product. In such eases the products are to be explained in terms of the further reactions of the hydroperoxide formed, or the wastage by other reactions of the radicals involved in the chain, or shortening of of the chain length as may be produced by catalysts. As examples, the oxidation of 'para ffins, of oletins and of acetaldehyde are discussed.
In the oxidation of n-decane, hydroperoxide is formed initially, but ketones and acids are the major products as oxidation proceeds. The ketones arc believed mainly to arise from the further reactions of the hydroperoxide, while the acids come from the reactions of the R0 2 - radicals and the instability of the RO-radicals produced.
The oxidation of certain oleflns produces epoxides as a major product, and a mechanism for this reaction is suggested. This involves the reaction of an R0 2 -radical with the olefinic double bond, which gives rise to epoxide and an RO-radical. Diversion of the R0 2 -radical in this way produces a low yield of hydroperoxide.
The metal-catalysed oxidation of acetaldehyde is briefly discussed. The products arc to be explained by the low chain length of the oxidation and the occurrence of reactions between radicals and metal ions.