Determination of the gas‐phase decomposition rate constants of heptyl‐1 and heptyl‐2 hydroperoxides C7H15OOH

Abstract

The gas‐phase decomposition of n‐heptyl‐1 and n‐heptyl‐2 hydroperoxides C₇H₁₅OOH, which split into two radicals C₇H₁₅O and OH, has been investigated in the temperature range of 250–360°C. The decomposition has been carried out in a hydrogen–oxygen mixture (the hydroperoxide represents about 50 ppm) so as to avoid secondary reactions between the formed radicals and the reactants. Although the H₂–O₂ mixture is not spontaneously reactive in our conditions, it operates the transformation, through a fast and well‐known process, of the OH radicals into HO₂ radicals and then into H₂O₂. However, C₇H₁₅O radicals are also transformed into HO₂ radicals and then into H₂O₂, but through an unknown process. To avoid heterogeneous reactions, vessel and probe are coated by B₂O₃ and then treated by the slow combustion of hydrogen at 510°C and 250 torr before the experiments are performed. As the reaction scheme is very simple, due to the use of the H₂–O₂ mixture, the determination of the evolutions of the HO₂ concentration (followed by electronic paramagnetic resonance) lead to the determination of the gas‐phase decomposition rate constant of hydroperoxides. For the n‐heptyl‐1 hydroperoxide the rate constant is and for the n‐heptyl‐2 hydroperoxide it is .