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Item Pulse Radiolysis Study of Protoferrihaem IX Intercalated in Sodium Dodecyl Sulphate Micelles(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (02), 1978) Evers, Edward L.; Jayson, Gerald G.; Swallow, A. JohnHaemin intercalated in sodium dodecyl sulphate (SDS) micelles exists as monomer in an organic sphere of dimensions similar to that of cytochrome-c and thus provides a model which is closer to the biological molecule than any which has been studied hitherto. Hydrated electrons reduce intercalated haemin at pH 9.2 with k = 5.2x 10° dm3 mol-1 s-1. CH3CHOH radicals reduce it at pH 9.2 with k = 5.6x 108 dm3 mol-1 s~* and at pH 4 with k = 1.6x 10’ dm3 mol-1 s-1. Reduction is accompanied by spectroscopic changes in the haemin molecule at both pH 9.2 and 4, but at pH 9.2 additional changes take place afterwards over periods of several milliseconds. At pH 4.0 there are no additional changes. The final spectrum attained in both cases corresponds to the formation of reduced haemin in 100 % yield. The additional changes taking place after reduction in mildly alkaline solution are found to have an activation energy of 66.6 kJ mol-1. They are independent of pH in the range 9.2-10.7, and of added electrolyte in the range 0.05-0.2 mol dm-3. They arc attributed to conversion of OH- in reduced haemin into H2O, perhaps by protonation by water: [OH-Fei”(por)-H20]= + ca-q -> [OH-Fe"(por)-H2O]- I h2o [H2O-Fel'(por)-H2O]' + OH-. Corresponding changes are not seen at pH 4 because the hacmin exists as [H2O-Feni(por)-H2O]1' at that pH.Item Pulse Radiolysis of Methanolic Solutions of Tetranitromethane(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1977, 73 (2), 1977) Johnson, David W.; Salmon, G. ArthurThe rate constant for the reaction of solvated electrons with tetranitromethane (TNM) was measured to be k6=(2.89 ± 0.20)× 1010 dm3 mol–1 s–1 at room temperature. Measurements on nitrous oxide saturated solutions containing TNM indicate that ·CH2OH radicals react rapidly with TNM forming an unstable intermediate C(NO2)4+˙CH2OH [graphic omitted] [X] [graphic omitted] C(NO2)–3+ H++ HCHO + NO2(9), for which k9a=(8.5 ± 0.4)× 109 dm3 mol–1 s–1 and k9b=(2.9 ± 0.1)× 106 s–1. The yields of nitroform anion (NF–) in argon and nitrous oxide saturated solutions of G(NF–)= 5.63 ± 0.05 and 6.45 ± 0.05 are equated to the scavengeable radical yields in these solutions. The difference is ascribed to reactions in spurs between e–s and CH3O˙ radical. The yields obtained are compared with those measured in γ-irradiated systems.Item pH Effects on the Pulse Radiolysis of Deoxygenated Aqueous Solutions of Sulphur Dioxide(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (1-6), 1974) Eriksen, Trygve E.Dilute deoxygenated aqueous solutions of sulphur dioxide and its related anions HSO–3 and SO2–3 in the pH-range 2–11 were pulse irradiated and the time dependence of the transient optical absorptions and electrical conductance recorded. Hydrogen atoms and OH radicals abstract hydrogen from HSO–3. Also OH radicals react with SO2 and SO2–3 to form the radical ion SO–3˙ with an absorption maximum at 255 nm. The SO–3˙ radical ions recombine to form sulphate (SO2–4) and dithionate (S2O2–6), the reaction rate and relative proportions of products being pH-dependent. In acid solutions the SO–2˙ radical ion with an absorption maximum at 360 nm is also formed, presumably by reaction of hydrogen atoms with sulphur dioxide. The SO–2˙ radical ions recombine to form dithionite (S2O2–4).Item Pulse Radiolysis Study of the Reactions of Hydrated Electrons with Naphthalene, Phenanthrene, Biphenyl and Fluorene in Aqueous Micellar Solutions(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (1-6), 1974) Fendler, Janos H.; Gillis, Hugh A.; Klassen, Norman V.The reaction of hydrated electrons with naphthalene, phenanthrene, biphenyl and fluorene to form the respective aromatic radical anions has been studied in aqueous solutions (1 % methanol, pH 12.1) in the presence and absence of micellar hexadecyltrimethylammonium bromide (CTAB). The reaction rates are 3-9 times faster in the presence of micellar CTAB suggesting that CTAB will, in general, enhance this type of reaction. An absorption spectrum of the free fluorene radical anion was obtained. In the presence of CTAB the aromatic radical anions decay to second transients which are probably the hydrogen adducts of the aromatic molecules.Item Kinetics of Ozone Formation in the Pulse Radiolysis of Oxygen+Ethylene Mixtures(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1973, 69 (5), 1973) Bevan, P. L. T.; Johnson, G. R. A.Pulse radiolysis of O2+ C2H4 mixtures has been used to determine the rate constant of the reaction O + O2+ M → O3+ M (M = C2H4) the values, obtained from the kinetics of O3 formation and from the dependence of the O3 yield on C2H4 concentration, being 6.5 ± 0.7 × 10–32 and 5.3 ± 0.5 × 10–32 cm6 molecule–2 s–1, respectively. Competition studies, in the absence and presence of SF6, show that C2H4 depresses the primary yield of O atoms from pulse-irradiated O2, the maximum depression by C2H4 being the same as that by SF6.Item Semiquinone Free Radicals and Oxygen: Pulse Radiolysis Study of One Electron Transfer Equilibria(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1973, 69 (4), 1973) Patel, Kantilal B.; Willson, Robin L.The absorption characteristics and acid dissociation constants of the semiquinone radicals of several methyl derivatives of benzoquinone and naphthoquinone have been determined by pulse radiolysis. Absolute rate constants for electron transfer from the superoxide-ion O–2 to mono- and di-methyl benzoquinones have been determined. In the case of duroquinone, evidence has been obtained for the occurrence of the equilibrium reaction: O–2+ duroquinone ⇌ O2+ durosemiquinone with Kc= 2.3 ± 0.2 × 10–2.Item Observations on Solvated Electrons in Aliphatic Hydrocarbons at Room Temperature by Pulse Radiolysis(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1973, 69 (4), 1973) Baxendale, J. H.; Bell, C.; Wardman, P.The spectra of solvated electrons (e–s) in n-hexane, cyclohexane, methylcyclohexane and isopentane at room temperature have been obtained. Electron-cation recombination reactions are second order and have rate constants 1–20 × 1014 M–1 s–1 at 20°C. The rate constants for the reaction of e–s with pyrene and carbon tetrachloride in n-hexane are 1.0 × 1012 M–1 s–1 and the latter reaction has an activation energy of 5 ± 1 kcal mol–1. The relationship of these observations to mobilities of electrons in hydrocarbons measured by conductivity is discussed.Item Yield of Excited Singlet and Triplet States in the Pulse Radiolysis of Toluene(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1973, 69 (4), 1973) Baxendale, J. H.; Rasburn, E. J.The 100 eV yield of the excited singlet state of toluene following a pulse of 10 MeV electrons is found to be 1.35, and the rate constant for its reaction with naphthalene to give the excited naphthalene singlet is 5.4 × 1010 M–1 s–1. The corresponding yield of the triplet state of toluene is 2.8 and assuming it reacts with naphthalene at a normal diffusion controlled rate, its half life is calculated to be 17 ns.Item Ketyl Radicals in Aqueous Solution Pulse Radiolysis Study(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1973, 69 (4), 1973) Adams, G. E.; Willson, R. L.The absorption spectra, extinction coefficients and acid dissociation constants of the ketyl radicals of benzophenone, acetophenone and its p-fluoro-, p-chloro-, p-bromo- and p-nitro-derivatives have been determined by pulse radiolysis. Rate constants for electron transfer from some simple organic radicals to the phenones were determined in alkaline solution. Studies with p-nitroacetophenone in neutral and alkaline solution show that both electron transfer and radical addition can take place, the relative proportion depending upon the structure of the radical.Item Pulse Radiolysis of 1,4-Dicyanobenzene inlAqueous Solutions in the Presence and Absence of Thallium(I) Ions(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1973, 69 (4), 1973) Robinson, E. A.; Schulte-Frohlinde, D.The rate constants for the reaction of 1,4-dicyanobenzene with the hydrated electron (k2= 2.4 × 1010 M–1 s–1), the hydroxyl radical (k2= 7.2 × 108 M–1 s–1) and the hydrogen atom (k2= 3.5 × 108 M–1 s–1) have been measured together with the spectra and extinction coefficients of the resulting adducts. By addition of methanol and of oxygen respectively it was possible to observe separately the adduct formed by the hydrogen atom and that formed by the hydroxyl radical. The radical anion of 1,4-dicyanobenzene, formed by reaction with the hydrated electron in neutral, de-aerated solution, can also be produced in acid solution if thallium(I) sulphate is present. Evidence is presented to show that the reduced form of the thallium(I) ions, Tl0 or Tl+2, which is formed in reaction with the H atom in acid solution, is capable of reducing 1,4-dicyanobenzene to give the anion at pH values as low as 0.01 (k(T1+2+ DCNB)= 2.7 + 109 M–1 s–1). Similar results have been obtained using 1,4-dinitrobenzene and it is suggested that addition of T1+ may find further applications as a method of producing radical anions in solution at low pH by pulse radiolysis.