An absolute- and relative-rate study of the gas-phase reaction of OH radicals and Cl atoms with n-alkyl nitrates

Rate constants for the reactions of OH radicals and Cl atoms with CH3ONO2, C2H5ONO2, n-C3H7ONO2, n-C4H9ONO2, and n-C5H11ONO2 have been determined at 298 +/- 2 K and a total pressure of approximately 1 atm. The OH rate data were obtained using both the absolute-rate technique of pulse radiolysis combined with kinetic spectroscopy and a conventional photolytic relative-rate method. The Cl rate constants were measured using only the relative-rate method. Evidence is presented from the kinetic studies that reaction of OH radicals with alkyl nitrates may involve both addition and abstraction pathways. The data show that the -ONO2 group substantially decreases the rate constant for H-atom abstraction by OH radicals from groups bonded to the -ONO2 group and also decreases that for groups in the beta-position. Similar results were found for the reaction of Cl atoms with these compounds. The results are discussed in terms of reactivity trends.