The Autoöxidizability of the Alkyl Groups in Xylene

Abstract

Abstract In the course of early experiments on the oxidation of rubber, it was observed that its solutions in commercial xylene, when exposed at 75° to a stream of oxygen, in presence of acetic anhydride (added to accelerate reaction) and a cobalt catalyst, gave m- and p-toluic acid, together with neutral liquids which were clearly not derived from the rubber. For instance, when a solution of 675 g. of rubber in 6075 g. of xylene was mixed with 844 cc. of acetic anhydride and 42 g. of cobalt naphthenate, and the mixture (in 4 batches) was treated at 75° for 2 days with a stream of oxygen, there were obtained, respectively, (1) by extraction of the xylene solution with 10% caustic alkali and (2) by subsequent distillation at approximately 1 mm. pressure of the volatile product from the residual xylene liquor, about 10 g. of crystalline acid and 80 g. of volatile neutral oxidation products. The acid was toluic acid (found: C, 70.6; H, 6.1; equiv., 135; calculated for C8H8O2: C, 70.55; H, 5.95%; equiv. 136), from which samples of both the m- and the p-isomeride (m. p. 110° and 176°, respectively) were isolated by fractional crystallization.