Photo-oxidation of Dimethyl Malonate Initiated by Chlorine Atoms in Gas Phase: Kinetics and Mechanism

The rate coefficient for the gas-phase reaction of chlorine atoms with dimethyl malonate (DMM, CH₃OC(O)CH₂C(O)OCH₃) was determined at 298 K using relative methods giving a value of (3.8 ± 0.4) × 10^-12, cm³ molecule^-1 s^-1). The photo-oxidation mechanism of DMM was also investigated. The main products were identified by infrared spectroscopy, and computational calculations were performed in order to support the experimental data. The results reveal that the photo-oxidation occurs mainly by the abstraction of an H atom from the methyl groups. The CH₃OC(O)CH₂C(O)OCH₂O^• radical formed subsequently reacts according to three competitive paths: reaction with molecular oxygen to yield CH₃OC(O)CH₂C(O)OC(O)H, isomerization-unimolecular decomposition to lead finally to CH₃OC(O)C(O)H, CO₂, and HC(O)OH, and α-ester rearrangement to form monomethyl malonate and carbon monoxide. The yield of products as a function of oxygen pressure was also determined.