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 = k12/k13. 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.

12C/13C kinetic isotope effects of the gas-phase reactions of isoprene, methacrolein, and methyl vinyl ketone with OH radicals

“…The gas chromatography combustion isotope ratio mass spectrometry (GCC-IRMS) technique used in this investigation is very similar to those described previously for the measurements of stable carbon isotope KIE values (Anderson et al, 2004a(Anderson et al, ,b, 2007aIannone et al, 2003Iannone et al, , 2008. KIE experiments are similar in concept to relative rate (RR) experiments.…”

“…n-alkanes + OH, alkenes + O 3 , etc. ), KIE values were fitted as a function of the inverse carbon number, N C -1 Iannone et al, 2003Iannone et al, , 2008Anderson et al, 2004aAnderson et al, ,b, 2007a. As can be seen from Figure To date, there are no previously published KIE values for the reactions of MVK and MACR with OH radicals.…”

“…The application of 13 C/ 12 C studies toward determining the photochemical history of the studied VOC requires knowledge of the isotopic fractionations associated with its chemical removal processes . Several experimental studies have contributed toward the development of a database of 13 C/ 12 C kinetic isotope effect (KIE) values associated with key gas-phase reactions Iannone et al, 2003Iannone et al, , 2008Anderson et al, 2004aAnderson et al, ,b, 2007a. All of the previous studies employed gas-chromatography combustion isotope ratio mass spectrometry (GC-IRMS) instrumentation to analyze gas-phase reaction mixtures from Teflon chambers.…”

Stable carbon isotope ratios of ambient secondary organic aerosols in Toronto

“…As the reaction progresses, the products will be enriched in 13 C due to the reaction of the parent VOC as well as that of the reaction product with the OH radical in the gas phase. Although the KIEs for reactions of nitrophenols have not been measured, they most likely will be normal KIEs, similar to all KIEs measured for reactions of light aromatic VOCs in the gas phase (Anderson et al, 2004). The overview of the results in Figs.…”

“…Irei et al (2015) reported that the main factor determining the carbon isotope ratio of the particulate phase products of toluene oxidation is the kinetic isotope effect (KIE) for the reaction of toluene with the OH radical and the carbon isotope ratio of the reacting toluene. The KIEs for the reactions of benzene, toluene and m-xylene with the OH radical have been measured in the laboratory (Anderson et al, 2004) and the carbon isotope ratio of their emissions in the Greater Toronto Area (GTA) have been determined by Rudolph et al (2002). Using these values, which are summarized in Ta- Table 3.…”