An experimental study of the gas-phase reaction of the NO3 radical with α,β-unsaturated carbonyl compounds

Abstract

The relative-rate technique has been used to obtain rate coefficients for the reaction between the NO₃ radical and α,β-unsaturated esters and ketones: methyl E-2-butenoate (k₁), methyl 3-methyl-2-butenoate (k₂), methyl E-2-methyl-2-butenoate (k₃), 3-methyl-3-buten-2-one (k₄), E-3-penten-2-one (k₅), 4-methyl-3-penten-2-one (k₆), and E-3-methyl-3-penten-2-one (k₇). The rate constants obtained by the relative-rate method at T = 298 ± 2 K and P = 760 ± 5 Torr (N₂ as bath gas) are: k₁ = (1.85 ± 0.56) × 10⁻¹⁵ cm³ molecule⁻¹ s⁻¹, k₂ = (1.41 ± 0.23) × 10⁻¹⁴ cm³ molecule⁻¹ s⁻¹, k₃ = (4.91 ± 1.15) × 10⁻¹⁴ cm³ molecule⁻¹ s⁻¹, k₄ = (8.27 ± 6.44) × 10⁻¹⁵ cm³ molecule⁻¹ s⁻¹, k₅ = (1.03 ± 0.31) × 10⁻¹⁴ cm³ molecule⁻¹ s⁻¹, k₆ = (1.44 ± 0.26) × 10⁻¹³ cm³ molecule⁻¹ s⁻¹ and k₇ = (1.55 ± 0.20) × 10⁻¹³ cm³ molecule⁻¹ s⁻¹. The rate constants are used to show the effect of increased substitution at the carbon–carbon double bond. Group-reactivity factors for the ketone and ester groups are also determined. Atmospheric lifetimes of the compounds against night-time attack by NO₃ are estimated.