Kinetic and Mechanism of the Photo-Oxidation of 2-Methoxyethanol with Chlorine Atoms in the Troposphere

The rate coefficient for the reaction between 2-methoxyethanol (2ME, CH₃OCH₂CH₂OH) and chlorine atoms in the gas phase has been determined for the first time by the relative method at 298 K and atmospheric pressure using infrared spectroscopy. This yielded a value of (1.4 ± 0.2) × 10^-10 cm³ molecule^-1 s^-1. A comparison of this value with that derived from the structure-activity relationship (SAR) shows good concordance, and a reactivity correlation analysis using the rate coefficients reported in the bibliography for similar compounds was also included. The degradation products initiated by the attack of chlorine atoms to the 2-methoxyethanol molecule were identified as 2-methoxyacetaldehyde, formic acid, methyl formate (41%), methyl 2-hydroxyacetate (2.5%), and 2-hydroxyethyl formate (20%). From these products and the kinetic analysis, the reaction mechanism was proposed. Finally, the environmental implications of 2-methoxyethanol emissions were analyzed, taking into account its reactivity with hydroxyl (HO^•) radicals and chlorine atoms as well as its POCP values. The results showed that the lifetime of 2ME is controlled by its reactivity with HO^• radicals.