Carbon kinetic isotope effects in the gas-phase reactions of aromatic hydrocarbons with the OH radical at 296 ± 4 K -: art. no. L15108

The carbon kinetic isotope effects (KIEs) of the room temperature reactions of benzene and several light alkyl benzenes with OH radicals were studied in a reaction chamber at ambient pressure using gas chromatography coupled with online combustion and isotope ratio mass spectrometry (GCC-IRMS). The KIEs are reported in per mil according to epsilon (parts per thousand)=(KIE-1) x 1000, where KIE=k(12)/k(13). The following average KIEs were obtained, (all in parts per thousand): benzene 7.53+/-0.50; toluene 5.95+/-0.28; ethylbenzene 4.34+/-0.28; o-xylene 4.27+/-0.05, p-xylene 4.83+/-0.81; o-ethyltoluene 4.71+/-0.12 and 1,2,4-trimethylbenzene 3.18+/-0.09. Our KIE value for benzene + OH agrees with the only reported value known to us [Rudolph et al., 2000]. It is shown that measurements of the stable carbon isotope ratios of light aromatic compounds should be extremely useful to study atmospheric processing by the OH radical.