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

Abstract

ABSTRACT. The 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 13 C/ 12 C KIE values are reported as ε values, where ε = (KIE -1) × 1000‰, and KIE = k 12 /k 13 . 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 OH ε(‰) = (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 OH ε values from this study, the inverse MM dependence changes only marginally to OH ε(‰) = (485±14)MM -1 . The addition of these isoprene OH ε values to a recently measured set of O3 ε values in an analogous study [Atmos. Environ. 2008, 42, 8728-8737] allows for estimates of the average change in the 12 C/ 13 C ratio due to processing in the troposphere.

Catalytic hydrogenation and oxidation of biomass-derived levulinic acid

“…Thus, decarboxylation of levulinic acid to produce butanone might be one of the key conversion steps from biomass-derived carbohydrates to versatile fuels. Methyl-vinyl-ketone (MVK) is a degradation product of isoprene (Trapp et al 2001;Iannone et al 2009) or the dehydration product of 4-hyfroxy-2-butanone, which is obtained from the condensation reaction of acetone and formaldehyde. It can react with O 3 in the atmosphere, leading to the OH radical (Aschmann et al 1996) and can be involved in the aza-Morita-Baylis-Hillman reactions (aza-MBH) of imines as a Michael acceptor (Gao et al 2006).…”

Observations of isoprene, methacrolein (MAC) and methyl vinyl ketone (MVK) at a mountain site in Hong Kong

“…A number of chamber studies have been carried out to examine the isoprene oxidation cycle [ Myoshi et al , 1994; Carter and Atkinson , 1996; Iannone et al , 2009; Navarro et al , 2011]. However, during daytime the evolution of isoprene chemistry in the real atmosphere is conceptually different from chamber experiments in that there is a continuous supply of isoprene [ Karl et al , 2009].…”

Stable carbon isotope ratios of toluene in the boundary layer and the lower free troposphere

“…Rudolph et al (2002) measured isotope ratios in atmospheric VOC close to their anthropogenic sources. Several laboratory studies investigated the kinetic isotope effects for reactions between VOC and different reactants (Anderson et al, , 2004aIannone et al, 2008Iannone et al, , 2009Farkas et al, 2003; including the temperature dependence of the kinetic isotope effects (Anderson, 2005;Gensch et al, 2011). By applying the concept of the hydrocarbon clock on J. Wintel et al: δ 13 C of toluene in the lower troposphere VOC isotopologues, stable carbon isotope ratios have also been used to determine the photochemical age of VOC in the atmosphere Rudolph et al, 2003;Saito et al, 2002Saito et al, , 2009).…”