Benzene in Auto Exhaust

The gas phase thermal decomposition rates of the C₁ and C₂-substituted peroxyacyl nitrates (RC(O)OONO₂), PAN (R = CH₃), PPN (R = C₂H₅) and vinyl-PAN (R = CH₂ = CH-) have been measured at ambient temperature (288 - 299 K) and 1 atm. of air. Our results for PAN (k = A exp (-E_a/RT), log₁₀ (A, s^-1) = 16.2 ± 1.6, E_a = 26.9 ± 2.1 kcal / mol, k₂₉₈ = 3.0 × 10^?4S^?1) are consistent with literature data. Thermal decomposition rates for PPN and vinyl-PAN are similar to that for PAN, with k₂₉₈ = 3.0 × 10^?4S^?1 for PAN, 3.4 × 10^?4S^?1 for PPN and 3.0 × 10^?4S^?1 for vinyl-PAN. Implications for the atmospheric persistence of PPN and vinyl-PAN as compared to that of PAN are briefly discussed.