An experimental study of the gas-phase reaction of the NO3 radical with alpha,beta-unsaturated carbonyl compounds.

The relative-rate technique has been used to obtain rate coefficients for the reaction between the NO3 radical and alpha,beta-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 (ks), 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) x 10(-15) cm3 molecule(-1) s(-1), k2 = (1.41 +/- 0.23) x 10(-14) cm3 molecule(-1) s(-1), k3 = (4.91 +/- 1.15) x 10(-14) cm3 molecule(-1) s(-1), k4 = (8.27 +/- 6.44) x 10(-15) cm3 molecule(-1) s(-1), k5 = (1.03 +/- 0.31) x 10(-14) cm3 molecule(-1) s(-1), k6 = (1.44 +/- 0.26) x 10(-13) cm3 molecule(-1) s(-1) and k7 = (1.55 +/- 0.20) x 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.