Direct Kinetic Study of the Reaction of Cl2•- Radical Anions with Ethanol at the Air−Water Interface

Abstract

This work focuses on the development and application of the UV diffuse reflectance−laser flash photolysis technique to directly study the kinetics of reactions occurring at the gas−liquid-phase boundary. The reaction of Cl2•- radical anion with ethanol was chosen to directly “probe” the reaction kinetics at the air−water surface. The reaction rates at the surface are shown to be more rapid than in the bulk liquid. Direct kinetic evidence is provided that the reaction of Cl2•- radical anion with ethanol is at least 2 times faster at the surface than in the bulk. The rate coefficient for the surface reaction Cl2•- + ethanol is found to be (4.45 ± 0.80) × 105 M-1 s-1. For comparison, the rate coefficient for the reaction of Cl2•- with ethanol in the aqueous phase is found to be (1.77 ± 0.34) × 105 M-1 s-1. The uncertainties in the above expressions are 2σ and represent precision only. The effective rate coefficient for the aqueous-phase reaction Cl2•- + ethanol is found to be consistent with what has been re...