FTIR kinetic study and products distribution of the reaction of CHCl2C(O)OCH3 with Cl atoms at 298 K and 760 Torr.

VIANNI G. STRACCIA C.; CYNTHIA B. RIVELA; MARIA BELEN BLANCO; IULIA PATROESCU-KLOTZ; ILLMANN NIKLAS; PETER WIESEN; MARIANO A. TERUEL

Renes

Simposio; 26th International Symposium on Gas Kinetics and Related Phenomena; 2022

The relative rate coefficient and products distribution of the gas-phase reaction of methyl dichloroacetate(CHCl2C(O)OCH3) with Cl atoms were obtained at 298 K and atmospheric pressure. All the experimentswere performed in a 480 L Pyrex glass atmospheric simulation reactor coupled with“in situ”FTIRspectroscopy. The rate coefficient obtained from the average of different experiments was: kCl = (3.31 ±0.50) ×10-13 cm3.molecule-1s-1. In addition, products studies were performed in similar conditions of thekinetic experiments. The initial pathway, for the degradation of methyl dichloroacetate in the reactionwith Cl atoms occur via H-atom abstraction at the alkyl groups. Dichloroacetic acid, phosgene, methyltrichloroacetate and carbon monoxide, were the main products identified and quantified. The productyields for the reaction studied were the following: (22±2; 19±3; 16±1 and 38±2) % for Cl2CHCOOH,COCl2, CO, and CCl3C(O)OCH3, respectively. Phosgene is an extremely toxic gas that can be graduallydegraded through UV-radiation to produce ClOx which has an important impact on the depletion ofozone layer. The atmospheric implications of the reaction investigated were assessed by the estimationof the tropospheric lifetimes of the chlorinated ester towards Cl atoms to be τCl= 10 years. In addition,other parameters were estimated to evaluate the possible environmental impact of the emissions ofMDCA to the air. The Ozone Depletion Potential obtained, (ODP) was 0.044. This fact reflects that therelative influence of this chlorinated organic compound on the destruction of the ozone layer issignificant lower than CFCl3. In addition, in order to evaluate the contribution to greenhouse warming,the Global Warming Potential, (GWP) was calculated to be 103, 28, 8 for times horizon of 20, 100 and500 years, respectively. This contribution to global warming is significant compared with CO2 due to itslong lifetime. At regional scale, compounds with Cl, F, N and S substituents may contribute to rainfallacidification. Consequenly, the Acidification Potential of the ester, (AP) was estimated using theempirical equation given by (de Leeuw, 1993),to be 0.45. This value indicates that methyldichloroacetate degradation may play some role in acidifying rainwater.On the other hand, the Photochemical Ozone Creation Potential, (POCP) was estimated for the titleVOC in 0.03, of negligible importance in the photochemical smog formation.References[1] Atkinson, R., Baulch, D.L., Cox, R.A., Hampson, R.F., Kerr, J.A., Rossi, M.J., Troe, J., J. Phys.Chem. Ref. Data 26, 521–1011, 1997.[2] Christensen, L.K., Ball, J.C., Wallington, T.J., J. Phys. Chem. A 104, 345–351, 2000.[3] Jenkin, M.E., Derwent, R.G., Wallington, T.J.,. Atmos. Environ. 163, 128–137, 2017[4] Kwok, E., Atkinson, R.,. Atmos. Environ. 29, 1685–1695, 1995[5] de Leeuw, F.A.A.M. Chemosphere 27, 1313–1328, 1993124