Carbon kinetic isotope effects in the gas‐phase reactions of aromatic hydrocarbons with the OH radical at 296 ± 4 K

Abstract

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 ɛ (‰) = (KIE − 1) × 1000, where KIE = k 12 / k 13 . The following average KIEs were obtained, (all in ‰): 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.