Gas Phase Kinetics and Mechanistic Insights for the Reactions of Cl atoms with Isopropyl Formate and Isobutyl Formate

Abstract

Rate coefficients for the reactions of Cl atoms with isopropyl formate (IPF) and isobutyl formate (IBF) were measured experimentally over the temperature range of 268–363 K and at 760 Torr of nitrogen using relative rate method. Ethyl acetate and ethyl formate were used as reference compounds for the measurement of rate coefficients for the reaction of IPF with Cl atoms. Ethane and ethylene were used as reference compounds for the measurement of rate coefficients for the reaction of IBF with Cl atoms. The obtained rate coefficients for the reactions of IPF and IBF with Cl atoms at 298 K are (1.56 ± 0.47) × 10–11 and (7.60 ± 1.10) × 10–11 cm3 molecule–1 s–1 respectively. The derived temperature dependent Arrhenius expression for the reactions of IPF and IBF with Cl atoms are k R1(268–363K) Experimental = (3.87 ± 0.88) × 10–12 exp [(418 ± 70)/T] and k R2(268–363K) Experimental = (1.83 ± 0.45) × 10–11 exp [(421 ± 70)/T] cm3 molecule–1 s–1 respectively. A qualitative analysis of the products formed during the reactions of Cl atoms with IPF and IBF were carried out using gas chromatography–mass spectrometry (GC–MS) and gas chromatography–infrared spectroscopy (GC–IR) as analytical tools, and the degradation mechanisms were proposed on the basis of end products. To rationalize our experimentally obtained results, computational calculations were performed to calculate the temperature dependent rate coefficients for these reactions over the temperature range of 200–400 K at CCSD­(T)/cc-pVDZ//MP2/6-31+G­(d, p) level of theory using canonical variational transition state theory (CVT) with small curvature tunneling (SCT). Detailed discussions on the thermochemistry of the reactions, branching ratios, and atmospheric implications are discussed in the manuscript.

Kinetic Studies on the Photo-oxidation Reactions of Methyl-2-methyl Butanoate and Methyl-3-methyl Butanoate with OH Radicals

“…However, the formation of 2-butanol cannot be nullified as it was observed in both GC-MS and GC-IR. A similar conclusion was made by Kumar and Rajakumar, 39 • radical. This radical is the most significant peroxy radical (∼50 Tmoles or 2500 Tg per year) in the Earth's atmosphere.…”

“…However, the formation of 2-butanol cannot be nullified as it was observed in both GC-MS and GC-IR. A similar conclusion was made by Kumar and Rajakumar, who have studied the reactions of isopropyl formate and isobutyl formate with Cl atom. In their study, they have mentioned the formation of methyl formate from the reaction of HC­(O)­O · radical with · CH 3 radical.…”

Tropospheric Photo-oxidation of Ethyl Methacrylate Initiated by Cl Atoms in the Gas Phase: Kinetic and Mechanistic Investigations

“…The concentrations of the reactants were measured by GC-FID with a maximum uncertainty of 5%. In detailed explanation for the calculation of error is given in our previous publication 37 and only major calculations are highlighted here. For each experimental trial, the slope and the corresponding error was calculated by linear least-squares method.…”