Henry's Law Constants of Some β-, γ-, and δ-Hydroxy Alkyl Nitrates of Atmospheric Interest

Abstract

Organic nitrates form via the photodegradation of hydrocarbons in the troposphere in the presence of NO and NO2. This process competes with the chemical cycle leading to ozone production since it sequesters both nitrogen oxides and organic radicals. Hydroxy nitrates form via the atmospheric reactions of alkanes and alkenes and are thought to be an important nitrogen oxides reservoir. In this study, new synthetic methods to produce β-, γ-, and δ-hydroxy nitrates of atmospheric interest were developed. NMR and IR spectroscopies were used to characterize these compounds. Henry's law coefficients of C4 and C5 hydroxy nitrates at 291 ± 2 K were measured using a dynamic equilibrium system. The solubility decreases with the organic chain length and increases with increasing distance between the nitrooxy and hydroxy groups. Due to their large Henry's law coefficients these species will partition into droplets in the presence of clouds and fogs. Measurements of the OH reaction and photolysis rate coefficients are needed for an accurate assessment of the atmospheric lifetimes of these compounds.

Observations of total alkyl nitrates during Texas Air Quality Study 2000: Implications for O3 and alkyl nitrate photochemistry

“…To assess the role of deposition, we continue with the ethene oxidation example and estimate a dry deposition velocity for 2-nitrooxyethanol and a boundary layer height such that this hydroxyalkyl nitrate has a lifetime to deposition of 8 hours. Such rapid deposition is a reasonable estimate as measurements show that hydroxyalkyl nitrates have large Henry's law coefficients [Shepson et al, 1996;Treves et al, 2000;Treves and Rudich, 2003] and our observations at La Porte show that both HNO 3 and SANs decrease with the same time constant of 5.5 hours in the afternoon. Rapid decay of hydroxyalkyl nitrates has also been observed in northern Michigan where isoprene nitrates decayed with a 4 hour lifetime [Grossenbacher et al, 2001].…”

Observations of total RONO<sub>2</sub> over the boreal forest: NO<sub>x</sub> sinks and HNO<sub>3</sub> sources

“…The measured Henry's law coefficients of some of the more soluble individual hydroxy nitrates (∼ 10 3 -10 5 M atm −1 , Shepson et al, 1996;Treves et al, 2000) are orders of magnitude lower than that of HNO 3 (1 × 10 14 M atm −1 at pH ∼ 6.5, Seinfeld and Pandis, 2006). Still, these measured Henry's law coefficients of hydroxy nitrates indicate that wet deposition is a significant loss process and a recent study indicates that foliar uptake of organic nitrates is possible (Lockwood et al, 2008 Min, personal communication, 2012).…”

“…Although Henry's law coefficients of small (≤ 5 carbons) hydroxy nitrates have been measured to be quite large, approximately ∼ 10 3 -10 5 M atm −1 (Shepson et al, 1996;Treves et al, 2000), it is reasonable to assume that as a ten carbon compound, a monoterpene nitrate may have a lower Henry's law coefficient. We therefore assume that these nitrates partition only into organic aerosol and that the organic aerosol contains sufficient liquid water for this reaction to occur (median RH of 63 % and minimum of 34 %).…”

A model for studies of tropospheric ozone and nonmethane hydrocarbons: Model description and ozone results

“…It is also possible that through the use of monthly mean input fields a correlation between the input parameters on shorter time scales is missed and biases the dry deposition calculation. It is thus desirable to calculate all these surface Used value for 5-nitroxy-2-butanol [Treves et al, 2000] and T-dependence of 1-nitroxy-2-butanol [Shepson et al, 1996]. i H eff used, K A = 1.74 Á 10 À5 [Lide, 1999].…”