Absolute rate constant measurements for the reaction of atomic hydrogen with acetone, 2-butanone, propionaldehyde and butyraldehyde in aqueous solution

Arrhenius parameters for the reaction of hydrogen atoms with acetone, 2-butanone, propionaldehyde, and butyraldehyde in aqueous solution have been directly measured by electron paramagnetic resonance free induction decay (FID) attenuation measurements. For these compounds, absolute scavenging rate constants at 25 deg C of (1.97 ± 0.10) x 106, (3.82 ± 0.32) x 107, (8.11 ± 0.47) x 107, and (1.14 ± 0.07) x 108 dm3 mol-1 s-1, with corresponding activation energies of 30.7 ± 1.3 (7.5-52.8 deg C), 40.1 ± 0.7 (8.1-74.5 deg C), 22.2 ± 0.9 (8.0-39.0 deg C) and 23.8 ± 0.8 (5.4-67.7 deg C) kJ mol-1 were measured, respectively. Competitive kinetic measurements have established that greater than 95% of H atom reaction with 2-butanone is by abstraction. (author). 29 refs., 1 tab., 3 figs