Kinetics and Mechanism of Acetone Cyclic Diperoxide (3,3,6,6-Tetramethyl-1,2,4,5-tetraoxane) Thermal Decomposition in Benzene Solution

Article abstract of DOI:10.1021/jo00186a005

In the temperature range of 135,5 to 165,0 deg C the main products of acetone cyclic diperoxide (ACDP) thermolysis in benzene solution are oxygen, acetone, and toluene, with minor yields of methyl isopropyl ether, methyl acetate, bibenzyl, methyl alcohol, methane, ethane, and carbon dioxide.The overall reaction follows a first-order kinetic law up to 60percent ACDP conversion.At temperatures ranging between 135,5 and 145,0 deg C the observed rate constant values are independent of the initial ACDP concentration, but at 150,5 and 165,0 deg C, with concentrations higher than 0,1 and 0,06 mol kg^-1, respectively, a nearly linear dependence between the rate constant and concentration can be established.The activation parameters for the ACDP unimolecular decomposition reaction are ΔH(excit) = 35,7 +/- 1,1 kcal mol^-1 and ΔS(excit) = 0,0 +/- 0,3 eu.Support for a stepwise mechanism instead of a concerted process is given by comparison of these parameters with those corresponding to alkyl peroxides and with the theoretically calculated activation energy for the ACDP homolysis.It is concluded that an induced decomposition of ACDP molecules by methyl radicals must be postulated in the thermolysis mechanism.That process, which gives oxygen, acetone, and methyl isopropyl ether as its products, has an estimated overall activation energy of 10 kcal mol^-1.In toluene solution at 165,0 deg C this reaction is supressed at ACDP initial concentration lower than 0,1 mol kg^-1.