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

The relative-rate technique has been used to obtain rate coefficients for the reaction between the NO3 radical and alpha,betaunsaturated esters and ketones: methyl E-2-butenoate (k(1)), methyl 3-methyl-2-butenoate (k(2)), methyl E-2-methyl-2-butenoate (k(3)), 3-methyl-3-buten-2-one (k(4)), E-3-penten-2-one (k(5)), 4-methyl-3-penten-2-one (k(6)), and E-3-methyl-3-penten-2-one (k(7)). The rate constants obtained by the relative-rate method at T = 298 +/- 2K and P = 760 +/- 5 Torr (N-2 as bath gas) are: k(1) = (1.85 +/- 0.56) x 10(-15) cm(3) molecule(-1) s(-1), k(2) = (1.41 +/- 0.23) x 10(-14) cm(3) molecule(-1) s(-1), k(3) = (4.91 +/- 1.15) x 10(-14) cm(3) molecule(-1) s(-1), k(4) = (8.27 +/- 6.44) x 10(-15) cm(3) molecule(-1) s(-1), k(5) = (1.03 +/- 0.31) x 10(-14) cm(3) molecule(-1) s(-1), k(6) = (1.44 +/- 0.26) x 10(-13) cm(3) molecule(-1) s(-1) and k(7) = (1.55 +/- 0.20) x 10(-13) cm(3) 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.