Rate of degradation of CH3CH=CHC(O)OCH=CH2 and CH3C(O)OCH=CHCH=CH2 in the troposphere

M. B .BLANCO, I. BEJAN, I. BARNES, P. WIESEN

Simposio; 22nd International Symposium on Gas Kinetics; 2012

Primary volatile organic compounds (VOCs) are emitted into the atmosphere from anthropogenic and biogenic (natural) sources. The fate and persistence of VOCs in the atmosphere is largely determined by their reactivity with different oxidant species present in the troposphere (generally OH radicals, NO3 radicals and O3 molecules). These reactions play an important role in determining the oxidation capacity and chemistry of the lower troposphere.1 The unsaturated esters vinyl crotonate (CH3CH=CHC(O)OCH=CH2) and 1-acetoxy-1,3-butadiene (CH3C(O)OCH=CHCH=CH2) are widely used in the production of polymers. Their copolymers are brittle resins, but they are used as cross-linking agents for other resins to raise the softening point and to increase abrasion resistance.2,3 The widespread industrial use of these esters on a large scale unavoidably results in fugitive emissions of the compounds to the atmosphere. As part of ongoing work to ascertain the atmospheric chemistry of esters, rate coefficients for the gas-phase reactions of vinyl crotonate and 1-acetoxy-1,3-butadiene with OH and NO3 radicals and O3 have been measured using a relative kinetic method. All the experiments were performed at room temperature (298±2 K) and atmospheric pressure in a 480 l cylindrical borosilicate glass photoreactor and in situ FTIR analysis was used to monitor the concentration-time behavior of the esters and the hydrocarbon reference compounds.3 The trans isomer of vinyl crotonate was investigated whereas the sample of 1-acetoxy-1,3-butadiene was a mixture of trans and cis isomers. The following rate coefficients (in units of cm3 molecule-1s-1) have been obtained for the reactions of vinyl crotonate with the oxidants: kOH = (4.49  1.05) × 10-11, kNO3 = (2.12  0.53) × 10-14 and kO3 = (0.98  0.34) × 10-17. For the corresponding reactions of 1-acetoxy-1,3-butadiene the following values were obtained: kOH = (9.07  0.30) × 10-11, kNO3 = (3.17  0.57) × 10-14 and kO3 = (2.71  0.64) × 10-17. To the best of our knowledge, this work represents the first experimental kinetic study of the reactions of OH and NO3 radicals and O3 molecules with vinyl crotonate and 1-acetoxy-1,3-butadiene. The kinetic data will be presented and discussed in terms of reactivity trends for reactions of atmospheric oxidants with unsaturated compounds. The implications of the results for the fate of the esters in the troposphere will also be addressed. References (1)Finlayson-Pitts, B. J.; Pitts , J. N. Jr. Chemistry of the Upper and Lower Atmosphere: Theory, Experiments, and Applications 2000, Wiley, New York. (2)Su, T.; Liao, J.; Guo, L.; La, M. Technology Development Chemical Industry, 2007, 3, 26-29. (3)www.basf.com (4)Barnes, I.; Becker, K.H.; Mihalopoulos, N. J. Atmos. Chem. 1994, 18, 267-289.