Rates and products have been determined for the thermal decomposition of sec-butyl peroxide at 110–150 °C in several solvents.The decomposition was shown to be unimolecular with energies of activation in toluene, benzene, and cyclohexane of 35.5 ± 1.0, 33.2 ± 1.0, 33.8 ± 1.0 kcal/mole respectively. The activation energy of thermal decomposition for the deuterated peroxide was found to be 37.2 + 1.0 kcal/mole in toluene.About 70–80% of the products could be explained by known reactions of free alkoxy radicals, and very little, if any, disproportionation of two sec-butoxy radicals in the solvent cage could be detected.The other 20–30% of the peroxide yielded H2 and methyl ethyl ketone. The yield of H2 was unaffected by the nature or the viscosity of the solvent, but H2 was not formed when s-Bu2O2 was photolyzed in toluene at 35 °C nor when the peroxide was thermally decomposed in the gas phase.α,α′-Dideutero-sec-butyl peroxide was prepared and decomposed in toluene at 110–150 °C. The yield of D2 was about the same as the yield of H2 from s-Bu2O2, but the rate of decomposition (at 135 °C) was only 1/1.55 as fast.Mechanisms for hydrogen production are discussed, but none satisfactorily explains all the evidence.
