Radical reactions initiated by chelate complexes of transition metals. VII. Effect of some copper chelates on the decomposition of cumene hydroperoxide in benzene

The kinetics of cumene hydroperoxide (CHP) decomposition in benzene in the presence of bis‐(‐)‐ephedrine copper(II) chelate (Cueph), copper acetylacetonate (Cuac), and copper oxinate (Cuox) was studied by chemical analysis, UV, and ESR measurements. It was found that only Cueph markedly accelerated the CHP decomposition. The course of the CHP decomposition in presence of Cueph may be described by the kinetic equation for bimolecular reactions. From the temperature dependence an activation energy of 17.3 kcal· mole −1 for CHP decomposition has been calculated. For the decay of paramagnetic Cu 2⊕ particles concentration during CHP decomposition in the presence of Cueph a reaction order of 1.1 with respect to [CHP] and 0.35 order kinetics for [Cueph] as well as an activation energy of 13.2 kcal·mole −1 were established. It was found on the basis of UV spectroscopy that during CHP decomposition in the presence of Cueph a complex between CHP and Cueph as an intermediate product was formed. Thus for the equilibrium constant of complex formation a value of 32 1 · mole −1 was estimated. The kinetic results obtained have been explained on the basis of supposition that a regeneration cycle for cupric species is operative. The disagreement between the supposed existence of the regeneration cycle and the observed decay of paramagnetic Cu 2⊕ particles in the course of CHP decomposition in the presence of Cueph is the discussed.