Lee, W Baasandorj, M Stevens, PS Hites, RA 2024-01-21T05:33:19Z 2024-01-21T05:33:19Z 2021-09-01 2005-02-15 0013-936X https://pubs.kist.re.kr/handle/201004/136734 A novel technique has been developed to simultaneously monitor the kinetics of the OH radical-initiated oxidation of isoprene and formation and oxidation of its products (methyl vinyl ketone, methacrolein, 3-methylfuran, and formaldehyde) using online mass spectrometry. The kinetics of isoprene and its products were investigated at 323 K and at 1 atm total pressure. The responses of 30 representative ions for isoprene and its products were monitored during the reaction, and their concentration profiles were calculated by linear algebraic equations, which resolve the measured mass spectra of representative ions into the responses of individual target organics, and by calibrations, which converted the responses to individual target concentrations. Using this method, yields of methyl vinyl ketone, methacrolein, and 3-methylfuran at 323 K were measured to be 14.4 +/- 0.1%, 19.0 +/- 0.2%, and 2.9 +/- 0.2%, respectively, in excellent agreement with previously reported yields under NOx-free conditions. The reaction kinetics of isoprene and its oxidation products measured by the experimental procedure developed in this study were compared with those estimated by a kinetic model of isoprene oxidation. The observed methacrolein concentrations as a function of time were reproduced reasonably well by this model, while the observed methyl vinyl ketone concentration could be reproduced by including secondary reactions of some of the hydroperoxide products of isoprene oxidation. The observed 3-methylfuran concentrations could be reproduced using secondary cyclization reactions of some of the 1,4-hydroxycarbonyl products of isoprene oxidation. These results suggest that under low NO, conditions reactions of some of the hydroperoxides and hydroxycarbonyls produced from the OH-initiated oxidation of isoprene may be a significant source of methyl vinyl ketone and 3-methylfuran in the atmosphere. English AMER CHEMICAL SOC GAS-PHASE REACTIONS RATE CONSTANTS ORGANIC-COMPOUNDS TEMPERATURE PHOTOOXIDATION MECHANISM HYDROXYCARBONYLS EMISSIONS LIMONENE NOX Monitoring OH-initiated oxidation kinetics of isoprene and its products using online mass spectrometry Article 10.1021/es049438f 1 ENVIRONMENTAL SCIENCE & TECHNOLOGY, v.39, no.4, pp.1030 - 1036 ENVIRONMENTAL SCIENCE & TECHNOLOGY 39 4 1030 1036 scie scopus 000227001700016 2-s2.0-13844251922 Engineering, Environmental Environmental Sciences Engineering Environmental Sciences & Ecology Article GAS-PHASE REACTIONS RATE CONSTANTS ORGANIC-COMPOUNDS TEMPERATURE PHOTOOXIDATION MECHANISM HYDROXYCARBONYLS EMISSIONS LIMONENE NOX Isoprene OH radicals Atmospheric Oxidation Mass Spectrometry