Determination of the gas‐phase decomposition rate constants of heptyl‐1 and heptyl‐2 hydroperoxides C 7 H 15 OOH

The gas‐phase decomposition of n ‐heptyl‐1 and n ‐heptyl‐2 hydroperoxides C 7 H 15 OOH, which split into two radicals C 7 H 15 O 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 H 2 –O 2 mixture is not spontaneously reactive in our conditions, it operates the transformation, through a fast and well‐known process, of the OH radicals into HO 2 radicals and then into H 2 O 2 . However, C 7 H 15 O radicals are also transformed into HO 2 radicals and then into H 2 O 2 , but through an unknown process. To avoid heterogeneous reactions, vessel and probe are coated by B 2 O 3 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 H 2 –O 2 mixture, the determination of the evolutions of the HO 2 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\documentclass{article}\pagestyle{empty}\begin{document}$$(1.1 \pm 0.25) \times 10^{16} \exp - \left({\frac{{43,500 \pm 1000}}{{RT}}} \right){\rm s}^{{\rm - 1}}$$\end{document}and for the n ‐heptyl‐2 hydroperoxide it is\documentclass{article}\pagestyle{empty}\begin{document}$$(7 \pm 2) \times 10^{15} \exp - \left({\frac{{41,500 \pm 1000}}{{RT}}} \right){\rm s}^{{\rm - 1}}$$\end{document} .