A kinetics study of the reaction of OH radicals with two C₂ hydrocarbons: C₂H₄ and C₂H₂

The flash photolysis‐resonance fluorescence technique has been utilized to study the kinetics of hydroxyl radical reactions with ethylene and acetylene at 300 K over a wide range of experimental conditions. (1) OH+C₂H₄ →^k₁ Products (e.g., C₂H₅O), (2) OH+C₂H₂ →^k₁ Products (e.g.,C₂H₂O+H). The bimolecular rate constant for Reaction (1) was observed to increase from (2.24–5.33) × 10⁻¹² cm³ molecule⁻¹⋅ sec⁻¹ as the total pressure varied from (3–300) torr of helium. The rate of Reaction (2) was invarient with total pressure, and the value obtained for k₂ was (1.65±0.15) × 10⁻¹³ cm² molecule⋅sec⁻¹. The observed pressure dependency of Reaction (1) brings the existing literature values for k₁ into close agreement. Reaction (2) has been shown to be particularly sensitive to secondary processes and this is discussed in some detail.