INFIQC   05475
INSTITUTO DE INVESTIGACIONES EN FISICO- QUIMICA DE CORDOBA
Unidad Ejecutora - UE
artículos
Título:
Gas-phase oxidation of methyl crotonate and ethyl crotonate. Kinetic study of their reactions towards OH radicals and Cl atoms
Autor/es:
M. A. TERUEL, J. BENITEZ-VILLALBA, N. CABALLERO, M. B. BLANCO
Revista:
JOURNAL OF PHYSICAL CHEMISTRY A
Editorial:
AMER CHEMICAL SOC
Referencias:
Lugar: Washington; Año: 2012 vol. 116 p. 6127 - 6133
ISSN:
1089-5639
Resumen:
Rate coefficients for the reactions of hydroxyl radicals and chlorine atoms with methyl crotonate and ethyl crotonate have been determined at 298 K and atmospheric pressure. The decay of the organics was monitored using gas chromatography with flame ionization detection (GC-FID), and the rate constants were determined using the relative rate method with different reference compounds. Room temperature rate coeficcients were found to be (in cm3 molecule−1 s−1): k1(OH + CH3CHCHC(O)OCH3) = (4.65 ± 0.65) × 10−11, k2(Cl + CH3CH CHC(O)OCH3) = (2.20 ± 0.55) × 10−10, k3(OH + CH3CH CHC(O)OCH2CH3) = (4.96 ± 0.61) × 10−11, and k4(Cl + CH3CH CHC(O)OCH2CH3) = (2.52 ± 0.62) × 10−10 with uncertainties representing ±2σ. This is the first determination of k1, k3, and k4 under atmospheric pressure. The rate coefficients are compared with previous determinations for other unsaturated and oxygenated VOCs and reactivity trends are presented. In addition, a comparison between the experimentally determined kOH with kOH predicted from k vs EHOMO relationships is presented. On the other hand, product identification under atmospheric conditions has been performed for the first time for these unsaturated esters by the GC−MS technique in NOx-free conditions. 2-Hydroxypropanal, acetaldehyde, formaldehyde, and formic acid were positively observed as degradation products in agreement with the addition of OH to C2 and C3 of the double bond, followed by decomposition of the 2,3- or 3,2-hydroxyalkoxy radicals formed. Atmospheric lifetimes, based on of the homogeneous sinks of the unsaturated esters studied, are estimated from the kinetic data obtained in the present work.