Gas-phase reactions of hydroxyl radicals with alkyl nitrite vapours in H2O2+ NO2+ CO mixtures

Abstract

The yields of CO2 from the chain reaction in H2O2+ NO2+ CO + alkyl nitrite mixtures, in which OH is the chain carrier and alkyl nitrites induce a chain termination step, have been used to deduce rate constants (ks) for OH attack on alkyl nitrites (RONO) in the vapour phase at ambient temperatures. Values of ks/109 dm3 mol–1 s–1 as a function of R were determined as follows: 0.71 ± 0.12 (CH3), 1.15 ± 0.23 (C2H5), 1.56 ± 0.32 (n-C3H7), 3.41 ± 1.48 (n-C4H9), 3.89 ± 0.58 (sec-C4H9), 3.47 ± 0.52 (i-C4H9), 0.91 ± 0.15 (t-C4H9), all based on ks=(1.63 ± 0.16)× 109 dm3 mol–1 s–1 for OH + n-butane. The small increase in ks from R = CH3 to t-C4H9 is considered to support a recent postulate that both H-abstraction and NO-abstraction pathways are operative, at least for R = CH3.