The mechanism of thermolysis of acyloxydialkyl peroxides

A thermolysis mechanism with the concerted dissociation of two bonds, -OO- and -C-O-, and formation of carboxylic acid and two radicals (tert-butoxyl and acetyl) is suggested on the basis of kinetic measurements, studies of the decomposition products, and quantum-chemical modeling of the thermolysis of per oxides of the general formula (CH3)(3)C-OO-CH(CH3)OC(O)R. Concerted dissociation is proved by low thermolysis activation energies, negative activation entropies, the independence of the decomposition rate constant from medium viscosity, carboxylic acid formation (one mole per mole of reacted peroxide), and the special features of the structure of peroxides. The formation of the tert-butoxyl and acetyl radicals and carboxylic acid molecule is more favorable energetically than the other possible reaction directions.