Kinetics of reactions of OH with organic carbonyl compounds in aqueous solution

The OH radical plays an important role in tropospheric chemistry. The OH radical is a very strong oxidant and its reactivity contributes to the atmospheric degradation of volatile organic compounds in aqueous solution. In this work the temperature dependencies of the rate constants for the reactions of OH with the following organic carbonyl compounds, ( 1) methyl ethyl ketone (MEK), ( 2) acetonylacetone, ( 3) isobutyraldehyde, ( 4) ethyl formate and ( 5) diacetyl are studied. By means of laser. ash photolysis and applying a competition kinetics method the following Arrhenius expressions were obtained: Reaction of OH with methyl ethyl ketone : k(1)(T) = (5.1 +/- 0.6) x 10(11) exp (-1804 +/- 914/T) M-1 s(-1) Reaction of OH with acetonylacetone : k(2)(T) = (1.1 +/- 0.1) x 10(11) exp (-1485 +/- 542/T) M-1 s(-1) Reaction of OH with isobutyraldehyde : k(3)(T) = (3.0 +/- 0.1) x 10(10) exp (-700 +/- 347/T) M-1 s(-1) Reaction of OH with ethyl formate : k(4)(T) = (1.8 +/- 0.1) x 10(10) exp (-1194 +/- 447/T) M-1 s(-1) Reaction of OH with diacetyl : k(5)(T) = (4.3 +/- 0.3) x 10(12) exp (-2880 +/- 590/T) M-1 s(-1) The errors stated throughout this study are statistical errors for a confidence interval of 95%. Reaction mechanisms are discussed and Evans - Polanyi correlations are presented.