Liquid-Phase Oxidation of Para-Cymene: Nature of Intermediate Hydroperoxides and Relative Activity of the Alkyl Groups

Abstract

Using photochemical and emulsion pro­cedures, a study has been made of the liquid-phase oxida­tion of p-cymene with respect to the nature of the result­ing hydroperoxides and their decomposition products, and the relative extent of oxidative attack at the methyl and iso­propyl groups. Hydroperoxide decomposition was negligible in the photochemical oxidations at 60C, and the product was shown to consist of 20% primary and 80% tertiary hydroper­oxide by reduction of the total product and fractionation of the resulting alcohols. The following compounds were shown to be present in the emulsion oxidation product in addition to the above mentioned hydroperoxides: dimethyl-p-tolylcarbinol, p-methylacetophenone, p-isopropylphenylcarbinol, cumic acid, p-acetobenzoic acid, p-A-hydroperoxyisopropyl, benzoic acid, and p-(I-hydroxyisopropyl) benzoic acid. By chromatographic separation of the acids and reduction of the other products, the relative extent of attack at the two positions was shown to be 1:4, identical with that of the photochemical oxidation. Pure tertiary hydroperoxide has been obtained for the first time.