Atmospheric fate of two relevant unsaturated ketoethers: kinetics, products and mechanisms for the reaction of hydroxyl radicals with (<i>E</i>)-4-methoxy-3-buten-2-one and (1<i>E</i>)-1-methoxy-2-methyl-1-penten-3-one

Abstract

The kinetics of the gas phase reactions of hydroxyl radicals with two unsaturated ketoethers (UKEs) at (298±3) K and 1 atm of synthetic air have been studied for the first time using the relative-rate technique in an environmental reaction chamber by in situ Fourier-transform infrared spectroscopy (FTIR). The rate coefficients obtained using propene and isobutene as reference compounds were (in units of 10−10 cm3 molecule−1 s−1) as follows: kTMBO (OH + (E)-4-methoxy-3-buten-2-one)  =  (1.41±0.11) and kMMPO (OH + (1E)-1-methoxy-2-methyl-1-penten-3-one)  =  (3.34±0.43). In addition, quantification of the main oxidation products in the presence of NOx has been performed, and degradation mechanisms for these reactions were developed. Methyl formate, methyl glyoxal, peroxyacetyl nitrate (PAN) and peroxypropionyl nitrate (PPN) were identified as main reaction products and quantified for both reactions. The results of the present study provide new insights regarding the contribution of these multifunctional volatile organic compounds (VOCs) in the generation of secondary organic aerosols (SOAs) and long-lived nitrogen containing compounds in the atmosphere. Atmospheric lifetimes and implications are discussed in light of the obtained results.