Liquid—Phase Catalytic Oxidation of Para-Cymene

Abstract

A study has been made of the liquid-phase oxidation of p-cymene with air in the presence of cobalt naphthenate at temperatures 50, 105, and 160°C. A solid carboxylic acid product has been isolated and a chromatographic procedure developed for its quantitative separation into the following compounds: cumic acid, p-acetylbenzoic acid, p-(α -hydroxyisopropyl)benzoic acid, and p-(α-hydroperoxyisopropyl)benzoic acid. The hitherto unreported hydroperoxy-acid has been characterized by (a) neutralization equivalent, (b) peroxidic oxygen content, (c) reduction to the above mentioned hydroxy-acid, and (d) metal-catalyzed, decomposition to the hydroxy- and keto-acids. Two previously reported products of cymene oxidation, p-toluic acid and terephthalic acid, were not produced in the present study. Large amounts of tarry products were formed at the higher temperatures, and lower yields of the carboxylic acids were obtained.