KINETIC-STUDIES OF OH REACTIONS WITH A SERIES OF ACETATES

Absolute rate constants have been measured for the gas phase reactions of hydroxyl radicals with a series of aliphatic acetates: methyl acet ate (k(1)), ethyl acetate (k(2)), n-propyl acetate (k(3)), n-butyl ace tate (k(4)), and n-pentyl acetate (k(5)). Experiments were carried out using the pulsed laser photolysis-laser induced fluorescence techniqu e over the temperature range 243-372 K. The obtained kinetic data were used to derive the Arrhenius expressions, and since the Arrhenius plo ts were slightly curved they were fitted, using a three-parameter expr ession. The Arrhenius expressions obtained are: k(1) = (0.53 +/- 0.09) x 10(-12) exp[-(128 +/- 102)/T]; k(2) = (0.48 +/- 0.09) x 10(-12) exp [(397 +/- 103)/T]; k(3) = (1.03 +/- 0.12) x 10(-12) exp[(370 +/- 69)/T ]; k(4) = (2.10 +/- 0.28) x 10(-12) exp[(299 +/- 81)/T], and k(5) = (2 .75 +/- 0.46) x 10(-12) exp[(302 +/- 102)/T] (in units of cm(3) molecu le(-1) s(-1)). At room temperature, the rate constants obtained (in un its of 10(-12) cm(3) molecule(-1) s(-1)) were as follows: methyl aceta te, 0.32 +/- 0.03; ethyl acetate, 1.67 +/- 0.22; tt-propyl acetate, 3. 42 +/- 0.26; n-butyl acetate, 5.52 +/- 0.51; n-pentyl acetate, 7.34 +/ - 0.91. Our results are compared with the previous determinations and discussed in terms of structure-activity relationships.