Kinetics of free-radical reactions with monoterpenes in the aqueous phase mimicing atmospheric aerosol chemistry

Abstract

Second order rate constants for the reactions of hydroxyl radicals and sulfate radicals with monoterpenes in the aqueous-phase have been determined by electron pulse radiolysis and transient absorption spectroscopy using the linear accelerator facilities at the University ofNotre Dame. The two monoterpenes examined in this study were geraniol and camphor. The rate constant for geraniol reaction with the hydroxyl radical and sulfate radical were: k(295 K)(•OH) = (1.01 ± 0.02) x 1010 M-1s -1, and k(292 K)(SO4-) = (3.47 ± 0.09) x 10 9M-1s-1 respectively, the analogous camphor reaction value for the hydroxyl radical was k(292 K)(•OH) = (3.63 ± 0.17) x 109M-1s-1. Additionally, rate constants over the temperature range 283-313 K were measured, with the Arrhenius behavior was determined as: lnk(T)•OH+geraniol = -(13.3 X 103) 1/RT + 24.9, lnk(T) •SO4-+geraniol = -(14.3 x 103) 1/RT + 27.9, and lnk(T)•OH+camphor = -(7.00 x 103) 1/RT + 24.9. These functions were used to estimate the reactivity of these terpenes under tropospheric conditions