Product study of the gas-phase reactions of O3, OH and NO3 radicals with methyl vinyl ether

Abstract

Products of the atmospherically important reactions of methyl vinyl ether were investigated at room temperature and 1 bar of dry air using FTIR spectroscopy and a scanning mobility particle sizer instrument. In the presence of NO_x the reaction with OH radicals was found to lead to the formation of methyl formate (80.9 ± 8.2)% and formaldehyde (76.6 ± 7.9)% as the main products. In the absence of NO_x, the major products were methyl formate (50.2 ± 5.1)% and formaldehyde (57.0 ± 6.0)%. The main products of the reaction of methyl vinyl ether with O₃ were methyl formate (73.5 ± 7.5)%, formaldehyde (27.8 ± 6.6)%, hydroperoxymethyl formate (19.6 ± 6.2)%, methanol (5.4 ± 0.9)%, CO₂ (30.3 ± 6.1)% and CO (14.2 ± 1.5)%, the formation yield of OH radicals in this reaction was estimated to be (14 ± 7)%. The reaction of methyl vinyl ether with NO₃ radicals again led to formation of methyl formate (52.5 ± 6.3)% and formaldehyde (51.4 ± 6.2)% as the main products. All yields given here are on a molar basis, the fraction of carbon recovered in identified products was (79 ± 11)%C in the OH reaction, (88 ± 7)%C in the ozonolysis and (52 ± 9)%C in the NO₃ reaction. The formation of aerosol was observed in the ozonolysis, but not the OH or NO₃ radical reactions. The particle formation in the ozone reaction could be modelled assuming an aerosol consisting of a single component with a mass-based formation yield of (0.66 ± 0.13)% and a partitioning coefficient of (0.98 ± 0.27) m³ μg⁻¹. Other products were observed in low yields, and residual FTIR spectra of unidentified products are presented. Simple mechanistic degradation schemes are proposed to explain the observed products, and the results are discussed with regard to their implications for atmospheric processes.