“Oxidative degradation kinetics and mechanism of two biodiesel constituents ((Ethyl-2-methyl propionate (E2MP) and ethyl-2,2-dimethyl propionate (E22DMP)) initiated by Cl atoms”
R. Kaipara and B. Rajakumar. ACS Earth Space Chem. 2020, 4, 142-156.


The oxidative reaction kinetics and mechanism of Ethyl-2-methyl propionate (E2MP) and Ethyl-2, 2-dimethyl propionate (E22DMP) initiated by Cl atoms were investigated both experimentally and computationally. Temperature dependent kinetic studies on the reaction of E2MP and E22DMP with Cl atoms were measured using relative rate technique over the temperature range of 268-363 K and at 760 Torr. The rate coefficients of both the reactions at 298 K were measured (using IUPAC recommended reference rate coefficients) to be k_(E2MP+Cl)^(298 K)= (7.19±1.60) × 10-11 cm3 molecule-1 s-1 and k_(E22DMP+Cl)^(298 K)= (5.87±1.33) × 10-11 cm3 molecule-1 s-1 respectively. In addition to complement our experimental results, the kinetics were computed at CCSD(T)/MG3S//BHandHLYP/6-311+G(d,p) level of theory over the temperature range of 200-400 K using Canonical Variational Transition State theory (CVT) in conjunction with Small Curvature Tunneling (SCT) and Interpolated Single Point Energy (ISPE). Furthermore, the product degradation of the studied esters with Cl atoms were performed using Gas Chromatography coupled with Mass Spectrometry (GC-MS) and Gas Chromatography coupled with Infrared Spectroscopy (GC-IR), as analytical tools. The plausible product degradation mechanisms were proposed and carbonyl compounds were found to be the major products from the degradation of studied esters. Atmospheric life times of both the esters were estimated with respect to the concentrations of Cl atoms in both ambient and Marine Boundary Layer (MBL) conditions.