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Item Reaction between ethylene and O– ions on the surface of magnesium oxide(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1977, 73 (07), 1977) Taarit, Younes Ben; Symons, Martyn C. R.; Tench, Anthony J.Interaction between ethylene and O– centres on magnesium oxide surfaces gives a radical having a nearly isotropic hyperfine coupling to two equivalent hydrogen atoms (58 G), a very weak coupling to a single proton, and strong coupling to 13C which indicates nearly unit spin-density in a 2p orbital on a single carbon atom. These results agree with expectation for H2C[double bond, length as m-dash]Ċ– anions, isoelectronic with the relatively stable H2C[double bond, length as m-dash]N radical in every respect. We suggest that after initial abstraction to give H2C[double bond, length as m-dash]ĊH radicals (not detected), ionization of the acidic acetylenic type proton occurs but this remains hydrogen-bonded to the radical anion: H2C[double bond, length as m-dash]Ċ–—HO–. In contrast, reaction of ethylene oxide with F+s centres on the surface gave H2Ċ—CH2O– radicals.Item Hydrogenation of Ethylene on Metal Electrodes: Part 2.—Structure of the Adsorption Layer on Platinum at a Working Condition on Open Circuit(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (1-6), 1974) Fujikawa, Keikichi; Katayama, Akiko; Kita, HideakiThe structure of the adsorption layer was studied by the potential sweep method on a platinum electrode in 1 N HC104 solution saturated with a reaction gas of various compositions (mixtures of H2, C2H4 and He). Results show that the structure of the adsorption layer satisfies previous predictions on the rate-determining step and that the open circuit potential is determined by the equilibrium condition of the step, H++e_^H(ads). The large change in the hydrogen peak caused by standing the electrode in the solution is in agreement with the decay of the catalytic activity for the hydrogenation of ethylene.Item Polymerization of Ethylene on Chromium Oxide Catalysts: Part 4.—Infra-red Study of the Adsorption of Nitric Oxide and Ammonia on Active Catalyst(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1973, 69 (3), 1973) Eley, D. D.; Rochester, C. H.; Scurrell, M. S.Nitric oxide adsorbs on reduced supported chromium(VI) oxide catalyst to give infra-red bands at 1740, ca. 1800, and ca. 1860 cm-1. The band at ca. 1800 cm1 has been assigned to nitric oxide molecules coordinatively chemisorbed on Cr4i ions in the surface. The band at 1740 cm-1 is considered to result from a combination of separate bands at 1743 and 1738 cm-1 due to nitric oxide covalently bound to Cr3+ and Cr5+ sites respectively. The band at ca. 1860 cm 1 is similarly assigned to nitric oxide chemisorbed on two types of site. The adsorption of ammonia gave infra-red bands due to coordinatively bound ammonia at 3400 and 3300 cm-1 which were insensitive to the extent of reduction of the catalyst. Correlations between the intensities of the bands due to adsorbed nitric oxide and the activities of catalyst samples for the polymerization of ethylene support the conclusion that Cr5i ions are the active sites in the polymerization process. The polymerization reaction was poisoned by the pre-adsorption of nitric oxide or ammonia.Item Hydrogenation of Ethylene on Metal Electrodes: Part 1.—Reduction of Ethylene with Hydrogen at a Platinum Electrode on Open Circuit(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1973, 69 (3), 1973) Fujikawa, Keikichi; Kita, Hideaki; Miyahara, KoshiroReduction of ethylene with hydrogen was studied at a Pt electrode on open circuit in H2SO4 and HClO4 solutions. The reaction rate and the open circuit potential were followed as a function of the gas composition (C2H4+ H2+ He, 1 atm) and the acid concentration. The rate, v, is independent of the acid concentration and is expressed as v=kHkEPHPE/(kHPH+kEPE), where the k values are constants and PH and PE the partial pressures of H2 and C2H4. The ratio kE/kH is 5–6, which is the same value obtained for the ratio of the diffusion rate constant of C2H4 in solution to that of H2. The rate-determining step is the mass transfer step of H2 or of C2H4 depending on the condition, PH/PE < 5–6 or > 5–6, respectively. This conclusion is supported by the dependence of the open circuit potential on the gas composition. Time variation of the catalytic activity of the activated electrode is discussed in terms of the activity change of the adsorbed hydrogen atom. Newly formed adsorbed hydrogen atoms are reactive, but after remaining on the surface, some of them become stable and have a retarding effect on the reaction.Item Electro-Catalytic Reduction of Ethylene on Platinum and Ruthenium(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (2), 1972) Byrne, M.; Kuhn, A. T.The kinetics of the cathodic reduction of ethylene on platinum and ruthenium in aqueous acid and alkali solutions are reported. The reduction proceeds according to the stoichiometric equations C2H4+ 2H++ 2e → C2H6(acid), or C2H4+ 2H2O + 2e → C2H6+ 2OH–(alkali). Tafel slopes, reaction orders in hydrogen ion and ethylene together with temperature effects have been determined by steady state potentiostatic techniques combined with chromatographic analysis. Two types of limiting current were observed under different conditions (i) a limiting diffusion current and (ii) a reaction limiting current associated with ethylene desorption from the electrode which leads to a maximum in the (potential-current) plots. Steady state parameters taken in conjunction with coverage measurements obtained from linear anodic sweeps indicate that the overall rate of reaction is controlled by the step C2H4(ads)+ H(ads)→ C2H5(ads)Item Kinetics of the Reactions of Hydrogen Atoms with Ethylene and Vinyl Fluoride(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (7), 1972) Teng, L; Jones, W. E.Hydrogen atoms generated in a Wood-Bonhoeffer discharge were reacted with vinyl fluoride and ethylene. The products of the vinyl fluoride reaction were: HF, C2H4, C2H6, C2H2, CH4, C3H6, n-C4H10 and C3H8. With the exception of HF, all were quantitatively studied over the temperature range 303-603 K. The reaction of ethylene under similar conditions gave: C2H6, C3H8, n-C4Hi0 and CH4. The kinetics and mechanisms of both reactions have been studied in detail. The rate constants have been calculated for each step of the mechanisms for three temperatures allowing determination of activation energies. The calculation of the rate constants and testing of the mechanisms was accomplished by numerical integration of the simultaneous differential equations for each species involved in the reactions.