Decomposition of cumene hydroperoxide (CHP) in benzene, chlorobenzene, and carbon tetra-chloride in the presence of magnesium 2-ethylhexanoate has been investigated. It has been determined and kinetically proved that the degradation is preceded by the formation of an intermediate hydroperoxide-catalyst complex; the thermodynamic parameters of the complex formation have been determined. It has been found that the catalytic activity of magnesium 2-ethylhexanoate in carbon tetrachloride is higher than in chlorobenzene and benzene. The stability of the complex depending on the nature of the solvent decreases in the order C6H5Cl > CCl4 > C6H6.