Products of the OH radical-initiated reactions of 2- and 3-hexyl nitrate

Products of the gas-phase reaction of OH radicals with 2-hexyl nitrate (containing 13% 3-hexyl nitrate) have been investigated by gas chromatography with mass spectral and flame ionization detection, and by direct air sampling atmospheric pressure ionization tandem mass spectrometry. The products identified and quantified from 2-hexyl nitrate were: 2-hexanone (8.6 ± 1.3%), propanal (3.4 ± 0.8%), butanal (2.3 ± 0.6%) and 5-hydroxy-2-hexanone (25%), where the molar yields are given in parentheses. 3-Hexanone was observed from the 3-hexyl nitrate reaction, with a molar formation yield of 9.5 ± 2.1%. Organic nitrates of molecular weight 133, 161, 177 and 208 were also observed, and these are attributed to C4-carbonyl nitrate(s), C6-carbonyl-nitrates, C6-hydroxycarbonyl-nitrates and C6-dinitrates, respectively, and are expected to account for all or most of the non-quantified reaction products from OH + 2- and 3-hexyl nitrate. 5-Hydroxy-2-hexanone formation indicates that the CH3CH(ONO2)CH2CH2CH(O)CH3 alkoxy radical dominantly reacts by isomerization.

► Multifunctional nitrates are major products from OH radical reaction with 2- and 3-hexyl nitrate.
► Alkoxy radical reactions determine if the NOx in the alkyl nitrate is released by OH reaction.
► The CH3CH(ONO2)CH2CH2CH(O)CH3 alkoxy radical from 2-hexyl nitrate dominantly isomerizes.