Kinetics of the reaction of hydroxyl radicals with ethylene and with C3 hydrocarbons

Abstract

The rates of reaction of hydroxyl radicals with ethylene, propane, propylene, methylacetylene, and allene have been measured at room temperature in a discharge-flow system using electron spin resonance detection. The stoichiometries (n=Δ[OH]/Δ[R]) were obtained by mass spectrometric analysis of the reacted gas under similar, although not completely identical conditions. The primary rate constants for the C₃-hydrocarbons obtained by combining the two are given as: OH + propane k₆=(5.0 ± 1.0)× 10¹¹ cm³ mol^–1 s^–1+ propylene k₇=(3.0 ± 1.0)× 10¹² cm³ mol^–1 s^–1+ methylacetylene k₈=(5.7 ± 1.0)× 10¹¹ cm³ mol^–1 s^–1+ allene k₉=(2.7 ± 1.5)× 10¹² cm³ mol^–1 s^–1. The values of n as well as the nature of the products provide some information on the mechanisms involved. A value of k₅=(1 ± 0.3)× 10¹² cm³ mol^–1 s^–1 was obtained for the reaction of OH + ethylene.