The temperature dependence of the OH radical reactions with some aromatic compounds under simulated tropospheric conditions

Abstract

AbstractThe 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 simulated atmospheric conditions over the temperature range 258–373 K. The relative rate coefficients obtained were placed on an absolute basis using evaluated rate coefficients for the corresponding reference compounds. Based on the rate coefficient k(OH + 2,3‐dimethylbutane) = 6.2 × 10−12 cm3 molecule−1s−1, independent of temperature, the rate coefficient for toluene kOH = 0.79 × 10−12 exp[(614 ± 114)/T] cm3 molecule−1 s−1 over the temperature range 284–363 K was determined. The following rate coefficients in units of cm3 molecule−1 s−1 were determined relative to the rate coefficient k(OH + 1,3‐butadiene) = 1.48 × 10−11 exp(448/T) cm3 molecule−1 s−1: o‐cresol; kOH = 9.8 × 10−13 exp[(1166 ± 248)/T]; 301–373 K; p‐cresol; kOH = 2.21 × 10−12 exp[(943 ± 449)/T]; 301–373 K; and phenol, kOH = 3.7 × 10−13 exp[(1267 ± 233)/T]; 301–373 K. The rate coefficient for benzaldehyde kOH = 5.32 × 10−12 exp[(243 ± 85)/T], 294–343 K was determined relative to the rate coefficient k(OH + diethyl ether) = 7.3 × 10−12 exp(158/T) cm3 molecule−1 s−1. The data have been compared to the available literature data and where possible evaluated rate coefficients have been deduced or updated. Using the evaluated rate coefficient k(OH + toluene) = 1.59 × 10−12 exp[(396 ± 105)/T] cm3 molecule−1 s−1, 213–363 K, the following rate coefficient for benzene has been determined kOH = 2.58 × 10−12 exp[(−231 ± 84)/T] cm3 molecule−1 s−1 over the temperature range 274–363 K and the rate coefficent for m‐cresol, kOH = 5.17 × 10−12 exp[(686 ± 231)/T] cm3 molecule−1 s−1, 299–373 K was determined relative to the evaluated rate coefficient k(OH + o‐cresol) = 2.1 × 10−12 exp[(881 ± 356)/T] cm3 molecule−1 s−1. The tropospheric lifetimes of the aromatic compounds studied were calculated relative to that for 1,1,1‐triclorethane = 6.3 years at 277 K. The lifetimes range from 6 h for m‐cresol to 15.5 days for benzene. © 1995 John Wiley & Sons, Inc.