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

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2020-01, Vol.124 (1), p.229-239
• Main Authors: Jara-Toro, Rafael A, Barrera, Javier A, Aranguren-Abrate, Juan P, Taccone, Raúl A, Pino, Gustavo A
• Format: Article
• Language: English
• Subjects: Physics
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/acs.jpca.9b10426

In this work, we investigate the degradation process of 1-chlorobutane, 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-2-butanone, 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 cm3 molecule–1 s–1) is in good agreement with the experimental value (2.22 ± 0.50) × 10–12 cm3 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.