Rate Coefficient and Mechanism of the OH-Initiated Degradation of 1-Chlorobutane: Atmospheric Implications

Abstract

In this work, we investigate the degradation process of 1chlorobutane, initiated by OH radicals, under atmospheric conditions (air pressure of 750 Torr and 296 K) from both experimental and theoretical approaches. In the first one, a relative kinetic method was used to obtain the rate coefficient for this reaction, while the products were identified for the first time (1-chloro-2-butanone, 1-chloro-2-butanol, 4-chloro-2butanone, 3-hydroxy-butanaldehyde, and 3-chloro-2-butanol) using mass spectrometry, allowing suggesting a reaction mechanism. The theoretical calculations, for the reactive process, were computed using the BHandHLYP/6-311++G(d,p) level of theory, and the energies for all of the stationary points were refined at the CCSD(T) level. Five conformers for 1-chlorobutane and 33 reactive channels with OH radicals were found, which were considered to calculate the thermal rate coefficient (as the sum of the site-specific rate coefficients using canonical transition state theory). The theoretical rate coefficient (1.8 × 10 −12 cm 3 molecule −1 s −1 ) is in good agreement with the experimental value (2.22 ± 0.50) × 10 −12 cm 3 molecule −1 s −1 determined in this work. Finally, environmental impact indexes were calculated and a discussion on the atmospheric implications due to the emissions of this compound into the troposphere was given.

Understanding the active role of water in laboratory chamber studies of reactions of the OH radical with alcohols of atmospheric relevance

“…19 The selected methodology was previously shown to render satisfactory results for the modelling of oxidation reactions of volatile organic compounds, [20][21][22] and was also tested in previous work by our group. 14,23…”