Autoxidation of Cyclohexane and Decomposition of Cyclohexyl Hydroperoxide in the Presence of Metaboric Acid

Abstract

The autoxidation of cyclohexane and the decomposition of cyclohexyl hydroperoxide (CHP), which was regarded as an intermediate of the autoxidation, were studied in the presence of metaboric acid and orthoboric acid ester in various solvents.
It was found that the addition of the metaboric acid brought about considerable effects on the composition of the decomposition products, as well as an acceleration ef the decomposition of CHP (Table 1 and 2).
The decompositlon rate of CHP in the presence of metaboric acid was of storde and of zero-order with respect to the concentration of CHP and the apparent concentration of metaboric acid, respectively.
The rate constant k in the presence of metaboric acid in dodecane at 120-160C was as follows (Fig.2) k=3.31x10 11exp(-25.7x10 3/RT)min-1
The decomposition rates of CHP in aromatic solvents were faster than those in paraflinic solvents (Fig.1). Ortheboric acid ester showed no catalytic activity in the decomposition of CHP (Table 2).
Main products obtained by the decomposition of CHP in the presence of metaborie acid were cyclohexanol boric acid esters and small amount of cyclohexanone. Besides, alcohol boric acid esters and small amount of ketones, due to the oxidation of solvent, were also formed. A similar tendency was observed in the autoxidation of cyclohexane in the presence of metaboric acid (Table 3). It was considered that in the case of the autoxidation of cyclohexane in the presence of metaboric acid, cyelohexanol boric acid esters and active oxygen were formed by the reaction of CHP with metaboric acid.