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Item Self-reactions of Isopropylperoxy Radicals in the Gas Phase(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (09-12), 1978) Kirsch, Leslie J.; Parkes, David A.; Waddington, David J.; Woolley, AllanThe photo-oxidation of 2,2′-azopropane has been studied in order to determine the overall rate constant for the second-order removal of isopropylperoxy radicals. Arrhenius parameters of log10(Aobs/dm3 mol–1 s–1)= 9.15 ± 0.03 and Eobs= 18.65 ± 0.50 kJ mol–1 have been determined over a temperature range 300–373 K. These values are compared with those obtained for the self-reactions of primary and tertiary alkylperoxyradicals, and the corresponding reactions in solution.Item Flash Photolysis Study of the Spectra of CH3O2 and C(CH3)3O2 Radicals and the Kinetics of their Mutual Reactions and with NO(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (07), 1978) Anastasi, Christopher; Smith, Ian W. M.; Parkes, David A.The ultraviolet spectra of the alkyl peroxy radicals, CH3O2 and C(CH3)3O2, have been obtained using flash photolysis with photoelectric recording. They are in good agreement with those found using molecular modulation spectroscopy. The overall rates of the “mutual” reactions: 2CH3O2→ products (3), and 2C(CH3)3O2→ products (4) also agree very well with rates found previously. Two other reactions of importance in low temperature oxidation have been studied. A lower limit of 10–12 cm3 molecule–1 s–1 was found for the rate constants of the overall reactions of CH3O2 and of C(CH3)3O2 with NO. The rate constant for the reaction between OH and t-butyl hydro-peroxide was found to be (3.0 ± 0.8)× 10–12 cm3 molecule–1 s–1 at room temperature.Item Oxygen Negative ton Reactions with Carbon Dioxide and Carbon Monoxide(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1973, 69 (1), 1973) Parkes, David A.Item Oxygen Negative Ion Reactions with Carbon Dioxide and Carbon Monoxide: Part 1(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (4), 1972) Parkes, David A.A drift tube and mass filter have been used to measure the rates of some O– negative ion molecule reactions, thought to be important in the radiolysis of carbon dioxide. Measurements of the clustering reaction O–+ CO2+ M → CO–3+ M in carbon dioxide give a third-order rate constant which falls with increasing pressure. This suggests an intermediate CO–3 ion with a lifetime of approximately 10–8 s. The limiting, low-pressure, rate constant is (1.1 ± 0.1)× 10–27 cm6 molecule–2 s–1 and, in the high-pressure limit, it is (2.7 ± 0.3)× 10–10 cm3 molecule–1 s–1. The rate also falls slowly with increasing reduced field. In O2 the rate constant is a factor of 3.5 lower, but it is difficult to measure the pressure dependence as accurately because CO–3 is also produced by the reaction: O–3+ CO2→ CO–3+ O2k=(5.5 ± 0.5)× 10–10 cm3 molecule–1 s–1. The rate constant measured in O2 for the associative detachment reaction O–+ CO → CO2+ e is (7.3 ± 0.7)× 10–10 cm3 molecule–1 s–1. Similar experiments in carbon dioxide are complicated by changes in the electron energy distribution as CO is added, but an upper limit of significantly less than 10–13 cm3 molecule–1 s–1 is suggested for the competing reaction: CO–3+ CO → 2CO2+ e. The reaction of O–3 with CO is very slow.Item Reactions of the O Negative Ion with Hydrogen and the Lower Hydrocarbons(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (4), 1972) Parkes, David A.The reactions between O–, formed by dissociative attachment to oxygen, and H2, D2, CH4, C2H6, C2H4 and C2H2 have been studied using a drift tube and mass filter. Gas densities ranged over a factor of five about 1017 molecule cm–3 and reduced fields were of the order of 3 × 10–16 V cm2 molecule–1. The reaction with the alkanes gave a single pair of products R + OH–, but the remainder produced both negative ions and free electrons. The following rate constants were measured and with the minor exception of OH– production from C2H4 were found to be substantially independent of the reduced field. [graphic omitted] The reaction with C2H4 also produced OH–, C2H–, C2OH– and C2H3O– at rates of 0.5 to 10, 5, 1.5 and 2 % respectively of the combined rate of the two major channels. The upper limits for the rates of the reactions of O–3 with the same molecules were two orders of magnitude lower.Item Negative Ion Reactions in Nitrous Oxide-I-Carbon Dioxide Mixtures(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (11), 1972) Parkes, David A.The rate constants have been measured for the following reactions in N2O + CO2 mixtures at pressures in the Torr region, using a drift tube and mass filter: NO–+ 2CO2→ CO2·NO–+ CO2, k9= 7.5 × 10–29 cm6 molecule–2 s–1, NO–+ CO2→ NO + CO2+ e, k10= 1.0 × 10–11 cm3 molecule–1 s–1, NO–+ CO2+ N2O → CO–3+ N2+ NO, k12= 1.0 × 10–27 cm6 molecule–2 s–1, → N3O–2+ CO2, or → CO2·NO–+ NO2O, k13= 1.5 × 10–28 cm6 molecule–2 s–1. The results obtained here confirm the importance of collisional detachment from NO– in N2O negative ion chemistry.Item Electron Attachment and Negative Ion-Molecule Reactions in Nitrous Oxide(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (11), 1972) Parkes, David A.The negative ions formed in N2O and N2O and N2O + O2 mixtures have been studied in the gas phase using a drift tube and mass filter. Gas pressures were in the Torr range, and reduced fields were varied between 10–17 and 10–15 V cm2 molecule–1. The observed ion spectrum was found to be governed by the following reaction, with their associated thermal rate constants: e + N2O → N2+ O–, k1= 4 × 10–15 cm3 molecule–1 s–1, O–+ N2O → NO–+ NO, k3=(1.95 ± 0.06)× 10–10 cm3 molecule–1 s–1, NO–+ N2O → NO–2+ N2, k4=(2.8 ± 0.2)× 10–14 cm3 molecule–1 s–1, NO–+ 2N2O → N3O–2+ N2O, k5=(8.5 ± 1.5)× 10–30 cm6 molecule–2 s–1, O–+ 2N2O → N2O–2+ N2O, k6=(4.2 ± 0.5)× 10–29 cm6 molecule–2 s–1, NO–+ N2O → N2O + NO + e, k11=(6.0 ± 1.0)× 10–12 cm3 molecule–1 s–1, O–2+ N2O → O–3+ N2, k10 < 10–12 cm3 molecule–1 s–1. The rates of reaction, (5), (6) and (11) were weak functions of reduced field. In no experiment was any evidence found for the existence of a long-lived N2O– ion.