OH reaction rate constants and UV absorption cross-sections of unsaturated esters

Abstract

Absolute rate coefficients have been determined for the gas-phase reactions of hydroxyl radicals with methyl acrylate ( k 1), methyl methacrylate ( k 2) and ethyl acrylate ( k 3). Experiments were performed using two different techniques, the relative rate method and the pulsed laser photolysis-laser induced fluorescence technique. The kinetic data obtained were used to derive the following Arrhenius expressions in the temperature range 253–374 K (in units of cm 3 molecule −1 s −1): k 1 = ( 2.0 ± 0.8 ) × 1 0 - 12 exp [ ( 553 ± 51 ) / T ] , k 2 = ( 2.5 ± 0.8 ) × 1 0 - 12 exp [ ( 821 ± 55 ) / T ] , k 3 = ( 2.3 ± 0.8 ) × 1 0 - 12 exp [ ( 580 ± 65 ) / T ] . At 298 K, the reaction rate constants obtained by the two methods were in good agreement. In addition, the UV absorption spectra for the three unsaturated esters have been determined at (298±2) K and the absorption cross-sections in the wavelength region 215–298 nm were reported. The results are presented, discussed and used to estimate the atmospheric lifetimes for the studied esters.