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Table C.1.

Summary of the reactions involving HONO.

Reaction ΔE α β γ F0 g Reference
kJ mol−1
1. H+ + HONO → HONO+ + H −235 0 Ionpol1, capture rate theory. We avoid introducing HONO+.
– → H2O + NO+ −693 1.0 2.0 × 10−9 5.27 3 0
2. He+ + HONO → HONO+ + He 0 Ionpol1, capture rate theory. We avoid introducing HONO+.
→ HO + NO+ + He 1.0 1.0 × 10−9 5.27 3 0
3. C + HONO → CO + NO + H −459 3.0 × 10−10 0 0 2 0 Capture rate theory, approximate branching ratio.
4. C+ + HONO → CO + NO+ + H −635 2.0 × 10−9 −0.4 0 3 0 Capture rate theory, approximate branching ratio. (HCO+ + NO is likely a non-negligible exit channel).
→ HCO+ + NO −817 0 −0.4 0 3 0
5. OH + HONO → NO2 + H2O −21 7.0 × 10−12 −0.6 0 1.6 10 This reaction has been studied between 278 and 373 K. The results from Jenkin & Cox (1987) show large uncertainty due to complicated secondary reactions. The results from Burkholder et al. (1992) show no barrier and a negative temperature dependency. We use an expression compatible with experimental data and leading to reasonable rate constant at 10 K.
6. HONO + H → H2ONO++ H2 −358 1.0 2.38 × 10−9 5.27 2 0 Ionpol1. The others isomers are also likely to be produced but we avoid introducing too many species without a notably different chemical behaviour.
→ HONOH+ + H2 −232 0
→ HONHO+ + H2 −196 0
7. HONO + HCO+ → H2ONO+ + CO −210 1.0 9.45 × 10−10 5.27 2 0 Ionpol1.
8. H2ONO+ + e− → HONO + H −524 2.0 × 10−7 −0.5 0 3 0 Rate by comparison with similar DR (Fournier et al. 2013; Florescu-Mitchell & Mitchell 2006; Geppert et al. 2004) and branching ratios deduced roughly from similar reactions using Plessis et al. (2012). The important fact is that HONO is likely a non-negligible product.
→ H2O + NO −825 1.0 × 10−7 −0.5 0 3 0
→ H + OH + NO −339 2.0 × 10−7 −0.5 0 3 0
→ H2O + N + O −207 1.0 × 10−7 −0.5 0 3 0
9. s-H + s-NO2 → s-HONO −317 0.7 0 Radical-radical reaction, well known in gas phase (Michael et al. 1979; Nguyen et al. 1998; Su et al. 2002). Both approach towards N and O atoms are attractive.
→ HNO2 −281 0.3 0
→ s-NO + s-OH −132 0
10. s-H + s-HONO → s-H2NO2 −163 1 2600 We use the theoretical work from Hsu et al. (1997). H2NO2 = (HN(O)OH). Some NO + H2O are likely to be produced but this exit channel involves a transition state close to the H + HONO entrance level.
→ s-H2 + s-NO2 −109 0
→ s-NO + s-H2O −301 0
→ s-HON + s-OH +164 0
11. s-H + s-H2NO2 → s-H3NO2 −302 1 0 M06-2X/AVTZ calculations (this work). H3NO2 = HO–NH–OH. Some HNO may be produced.
→ s-HON + s-H2O −159 0
→ s-HNO + s-H2O −327 0
12. s-OH + s-NO → s-HONO −185 1 0 The OH + NO reaction is a radical-radical barrierless reaction (Forster et al. 1995).

Notes. Exothermicities of the reactions (ΔE in kJ mol−1) are calculated at M06-2X/AVTZ level using Gaussian 2009 software. Definitions of α, β, γ, F0, g, Ionpol1 and Ionpol2 can been found in Wakelam et al. (2010, 2012): k = α × (T/300)β × exp(−γ/T) cm3 mol−1 s−1, T range is 10–300 K except in some cases (noted). Ionpol1: k = αβ(0.62 + 0.4767γ (300/T)0.5) cm3 mol−1 s−1, Ionpol2: k = αβ(1 + 0.0967γ(300/T)0.5 + (γ2/10.526) (300/T)) cm3 mol−1 s−1, F0 = exp(Δk/k0) (≈1 + (Δk/k0) and F(T) = F0exp(g ∣ 1/T − 1/T0∣).

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