Pressure and Temperature Dependence of Methyl Nitrate Formation in the CH3O2 + NO Reaction

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2012-06, Vol.116 (24), p.5972-5980
• Main Authors: Butkovskaya, Nadezhda, Kukui, Alexandre, Le Bras, Georges
• Format: Article
• Language: English
• Subjects: Chemical Sciences; Nitrates - chemical synthesis; Nitrates - chemistry; Nitric Oxide - chemistry; or physical chemistry; Peroxides - chemistry; Pressure; Temperature; Theoretical and
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp210710d

The branching ratio β = k 1b/k 1a for the formation of methyl nitrate, CH3ONO2, in the gas-phase CH3O2 + NO reaction, CH3O2 + NO → CH3O + NO2 (1a), CH3O2 + NO → CH3ONO2 (1b), has been determined over the pressure and temperature ranges 50–500 Torr and 223–300 K, respectively, using a turbulent flow reactor coupled with a chemical ionization mass spectrometer. At 298 K, the CH3ONO2 yield has been found to increase linearly with pressure from 0.33 ± 0.16% at 50 Torr to 0.80 ± 0.54% at 500 Torr (errors are 2σ). Decrease of temperature from 300 to 220 K leads to an increase of β by a factor of about 3 in the 100–200 Torr range. These data correspond to a value of β ≈ 1.0 ± 0.7% over the pressure and temperature ranges of the whole troposphere. Atmospheric concentrations of CH3ONO2 roughly estimated using results of this work are in reasonable agreement with those observed in polluted environments and significantly higher compared with measurements in upper troposphere and lower stratosphere.