The aerobic oxidation reaction of 1,2-dimethyl-4-isopropylbenzene to a hydroperoxide in the presence of N-hydroxyphthalimide and its derivatives has been studied. It has been found that up to a hydrocarbon (HC) conversion of 25-30%, the selectivity for the tertiary hydroperoxide of 1,2-dimethyl-4-isopropylbenzene is over 90-95%. A method for assessing the catalytic activity of phthalimide compounds in liquid-phase oxidation reactions of 1,2-dimethyl-4-isopropylbenzene with the use of quantum-chemically calculated values for the energies of singly occupied molecular orbitals (Delta D center dot (SOMO)) has been proposed.