Kinetic studies of OH reactions with a series of methyl esters

Absolute rate constants have been measured for the gas-phase reactions of hydroxyl radicals with a series of methyl esters: methyl propionate (k(1)), methyl butyrate (k(2)), methyl valerate (k(3)), and methyl caproate (k(4)). Experiments were carried out using the pulsed laser photolysis-laser induced fluorescence technique over the temperature range 253-372 K. The obtained kinetic data were used to derive the following Arrhenius expressions: k(1) (1.45 +/- 0.42) x 10(-12) exp[-(148 +/- 86)/T]; k(2) (0.96 +/- 0.29) x 10(-12) exp[(380 +/- 91)/T]; k(3) = (1.37 +/- 0.64) x 10(-12) exp[(401 +/- 142)/T]; k(4) (2.46 +/- 1.04) x 10(-12) exp[(326 +/- 130)/T] (in units of cm(3) molecule(-1) s(-1)). At room temperature, the rate constants obtained (in units of 10(-12) cm(3) molecule(-1) s(-1)) were as follows: methyl propionate (0.83 +/- 0.09); methyl butyrate (3.30 +/- 0.25); methyl valerate (4.83 +/- 0.55); methyl caproate (7.15 +/- 0.70). Our results are compared with the previous determinations and discussed in terms of structure-activity relationships.