Pressure and temperature dependence of the rate constants for the association reactions of vinoxy and 1-methylvinoxy radicals with nitric oxide

Abstract

The reactions of vinoxy, CH₂CHO and 1-methylvinoxy (acetonyl) CH₂C(CH₃)O radicals with NO and He as a bath gas have been investigated by experimental and theoretical methods as a function of temperature and pressure (0.8–920 mbar). Two classical techniques have been used for the experiments: the discharge flow (DF) and the laser flash photolysis (LFP) techniques, both associated with a monitoring of the radicals by laser induced fluorescence. Calculations of the potential energy surface were performed using ab initio molecular orbital theory at the G2 level. Derived molecular properties of the characteristic points of the potential energy surface were used to describe the mechanism and kinetics of the reactions under investigation. The nitroso-adducts, ON–CH₂CHO and ON–CH₂C(CH₃)O are predicted as the major addition products. Fall-off behavior of the reaction system was analyzed within the Troe formalism. The constructed fall-off curves allow a description of the reaction kinetics in wide ranges of pressure and temperature.

The following high and low pressure limiting rate constants have been obtained: