Iannone, RichardKoppmann, RalfRudolph, Jochen2010-01-222010-01-2209-MarAtmospheric Environment; 43, 3103-3110http://hdl.handle.net/10315/2916The stable-carbon kinetic isotope effects (KIEs) for the gas-phase reactions of isoprene, methacrolein (MACR), and methyl vinyl ketone (MVK) with OH radicals were studied in a 25 L reaction chamber at (298 ± 2) K and ambient pressure. The time dependence of both the stable-carbon isotope ratios and the concentrations was determined using a gas chromatography combustion isotope ratio mass spectrometry (GCC-IRMS) system. The volatile organic compounds (VOCs) used in the KIE experiments had natural-abundance isotopic composition thus KIE data obtained from these experiments can be directly applied to atmospheric studies of isoprene chemistry. All 13C/12C KIE values are reported as ε values, where ε = (KIE – 1) × 1000‰, and KIE = k12/k13. The following average stable-carbon KIEs were obtained: (6.56±0.12)‰ (isoprene), (6.47±0.27)‰ (MACR), and (7.58±0.47)‰ (MVK). The measured KIEs all agree within uncertainty to an inverse molecular mass (MM) dependence of OHε(‰) = (487±18)MM–1,which was derived from two previous studies [J. Geophys. Res. 2000, 105, 29329–29346; J. Phys. Chem. A 2004, 108, 11537–11544]. Upon adding the isoprene, MACR, and MVK OHε values from this study, the inverse MM dependence changes only marginally to OHε(‰) = (485±14)MM–1. The addition of these isoprene OHε values to a recently measured set of O3ε values in an analogous study [Atmos. Environ. 2008, 42, 8728–8737] allows for estimates of the average change in the 12C/13C ratio due to processing in the troposphere.GC-IRMSMethyl Vinyl KetoneMethacroleinIsopreneKinetic isotope effectArticlehttp://www.elsevier.com/wps/find/journaldescription.cws_home/246/description#descriptionhttp://www.elsevier.com/wps/find/journal_browse.cws_homehttp://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VH3-4VTKKX4-4&_user=866177&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1172730213&_rerunOrigin=google&_acct=C000045519&_version=1&_urlVersion=0&_userid=866177&md5=013255af887e744cbc14ef9d35e9ba4e