THE TEMPERATURE-DEPENDENCE OF THE OH RADICAL REACTIONS WITH SOME AROMATIC-COMPOUNDS UNDER SIMULATED TROPOSPHERIC CONDITIONS

The temperature dependence of the rate coefficients for the OH radical reactions with toluene, benzene, o-cresol, m-cresol, p-cresol, phenol , and benzaldehyde were measured by the competitive technique under si mulated atmospheric conditions over the temperature range 258-373 K. T he relative rate coefficients obtained were placed on an absolute basi s using evaluated rate coefficients for the corresponding reference co mpounds. Based on the rate coefficient k(OH + 2,3-dimethylbutane) = 6. 2 x 10(-12) cm3 molecule-1 s-1, independent of temperature, the rate c oefficient for toluene k(OH) = 0.79 x 10(-12) exp[(614 +/- 114)/T] cm3 molecule-1 s-1 over the temperature range 284-363 K was determined. T he following rate coefficients in units of cm3 molecule-1 s-1 were det ermined relative to the rate coefficient k(OH + 1,3-butadiene) = 1.48 x 10(-11) exp(448/T) cm3 molecule-1 s-1: o-cresol; k(OH) = 9.8 x 10(-1 3) exp[1166 +/- 248)/T]; 301-373 K; p-cresol; k(OH) = 2.21 x 10(-12) e xp[(943 +/- 449)/T]; 301-373 K; and phenol, k(OH) = 3.7 x 10(-13) exp[ (1267 +/- 233)/T]; 301-373 K. The rate coefficient for benzaldehyde k( OH) = 5.32 x 10(-12) exp[(243 +/- 85)/T], 294-343 K was determined rel ative to the rate coefficient k(OH + diethyl ether) = 7.3 x 10(-12) ex p(158/T) cm3 molecule-1 s-1. The data have been compared to the availa ble literature data and where possible evaluated rate coefficients hav e been deduced or updated. Using the evaluated rate coefficient k(OH toluene) = 1.59 x 10(-12) exp[(396 +/- 105)/T] cm3 molecule-1 s-1, 21 3-363 K, the following rate coefficient for benzene has been determine d k(OH) = 2.58 x 10(-12) exp[(-231 +/- 84)/T] cm3 molecule-1 s-1 over the temperature range 274-363 K and the rate coefficient for m-cresol, k(OH) = 5.17 x 10(-12) exp[(686 +/- 231)/T] cm3 molecule-1 s-1, 299-3 73 K was determined relative to the evaluated rate coefficient k(OH o-cresol) = 2.1 x 10(-12) exp[(881 +/- 356)/T] cm3 molecule-1 s-1. The tropospheric lifetimes of the aromatic compounds studied were calcula ted relative to that for 1,1,1-trichlorethane = 6.3 years at 277 K. Th e lifetimes range from 6 h for m-cresol to 15.5 days for benzene. (C) 1995 John Wiley & Sons, Inc.