| Popis: |
In the autoxidation of cumenes to benzoic acids at about 140° in butyric acid as solvent and with Co- and Mn-acetates as catalysts the main side-reaction is the formation of dimethylbenzyl alcohols. It may be suppressed by employing a low hydrocarbon concentration. The carbinols formed are partly dehydrated to α-methylstyrenes, which are oxidized, via acetophenones, to benzoic acids (about 50%), and to 1-methyl-1-phenylglycol derivatives, which are also oxidized — but less rapidly — to benzoic acids. Evidence is presented that the glycol derivatives are formed by interaction of the α-methylstyrenes and peroxy radicals. The solvent is attacked to some extent by the cobalt catalyst, yielding various degradation products. The first step in this reaction is assumed to be the attack of the trivalent Co-ions on the carboxyl group of the acid, yielding butyroyloxy radicals. A general scheme, describing the fate of an isopropyl group in the course of the autoxidation is given. |
