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 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 cm 3 molecule −1 s −1 , independent of temperature, the rate coefficient for toluene k OH = 0.79 × 10 −12 exp[(614 ± 114)/ T ] cm 3 molecule −1 s −1 over the temperature range 284–363 K was determined. The following rate coefficients in units of cm 3 molecule −1 s −1 were determined relative to the rate coefficient k (OH + 1,3‐butadiene) = 1.48 × 10 −11 exp(448/ T ) cm 3 molecule −1 s −1 : o ‐cresol; k OH = 9.8 × 10 −13 exp[(1166 ± 248)/ T ]; 301–373 K; p ‐cresol; k OH = 2.21 × 10 −12 exp[(943 ± 449)/ T ]; 301–373 K; and phenol, k OH = 3.7 × 10 −13 exp[(1267 ± 233)/ T ]; 301–373 K. The rate coefficient for benzaldehyde k OH = 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 ) cm 3 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 ] cm 3 molecule −1 s −1 , 213–363 K, the following rate coefficient for benzene has been determined k OH = 2.58 × 10 −12 exp[(−231 ± 84)/ T ] cm 3 molecule −1 s −1 over the temperature range 274–363 K and the rate coefficent for m ‐cresol, k OH = 5.17 × 10 −12 exp[(686 ± 231)/ T ] cm 3 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 ] cm 3 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.