Atmospheric chemistry of 2-ethyl hexanal: Photochemistry and oxidation in the presence of NO 2

Abstract

The photolysis and oxidation mechanism of 2-ethyl hexanal (C 4H 9CH(C 2H 5)C(O)H—2-Ethal) have been investigated. The UV absorption cross sections were recorded over the range 200–350 nm at 298 K. The quantum yield for photolysis at 254 nm was determined to be 0.51 ± 0.09. Photolysis of 2-Ethal occurs by two primary paths: a concerted elimination path and a radical formation path, the latter being the main path. CO, heptane, 3-heptanol, and 3-heptanone were identified as the main products. The rate constant for the reaction with Cl atoms was determined using the relative rate technique with isopentane and cyclohexane as reference gases. The average rate constant obtained was k = (2.8 ± 0.9) × 10 −10 cm 3 molecule −1 s −1. The most important path in the oxidation mechanism was the acyl radical forming channel, which was corroborated by the analysis of the products formed via photolysis in the presence of NO 2. Those products were CO 2, CO, peroxyacetyl nitrate, peroxypropionyl nitrate, and ethyl nitrate.