Journal Articles (before-1995)
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Item Critical Reflection of Neutrons A New Technique for Investigating Interfacial Phenomena(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1981, 77 (06), 1981) Hayter, J. B; Highfield, R. R; Pullman, B. JThe possibility of using neutron critical reflection for investigating interfacial phenomena is assessed. Calculations of the reflectivity of neutrons as a function of angle of incidence have been made for a variety of interfaces, using both an optical model and the Schrödinger equation. The information on the structure of the interfacial region that could be derived from reflectivity profiles is described for the following systems: fatty acid multilayers, black films, the liquid–vapour interface for a one-component system, the solution–vapour interface and the electrode–solution interface. Preliminary experiments have also been done to test the technique using thin films of deuterated stearic acid and copper on glass.Item Triplet State of 5-Nitro-2-furoic acid by Laser Flash Photolysis Spectrum, Lifetime and Reactivity(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1981, 77 (06), 1981) Kemp, Terence J; Martins, Luis J. ANanosecond laser flash photolysis (347.1 nm) of 5-nitro-2-furoic acid (NFA) in both polar and non-polar solvents at 295 K shows a transient absorption centred at 490 ± 5 nm with εca. 2 × 104 dm3 mol–1 cm–1 which is assigned to the lowest triplet excited state of NFA, denoted 3NFA. While λmax of 3NFA is independent of the solvent polarity, its lifetime is strongly solvent-dependent, being 22.7 ns in water and 274 ns in MeCN. Triplet–triplet energy transfer experiments showed the triplet energy ET to be 240 ± 4 kJ mol–1. 3NFA is extremely reactive, thus it abstracts a hydrogen atom from diphenyl-amine with k2=(8.64 ± 0.44)× 109 dm3 mol–1 s–1 and from diphenylmethanol with k2=(6.94 ± 0.55)× 107 dm3 mol–1 s–1, both in acetone solution. Representative of electron-transfer rates to 3NFA are those of CO2–3 and NNN′ N′-tetramethyl-p-phenylenediamine with k2=(1.56 ± 0.10)× 108 dm3 mol–1 s–1 and k2=(5.98 ± 0.20)′× 109 dm3 mol–1 s–1, respectively. The logarithm of the rate constant of oxidation of a series of electron donors by 3NFA correlates well with the corresponding electrode potentials up to the diffusion limit, although the figure for F– notably fails to fit the plot. The reduction potential of 3NFA is estimated to be 2.17 V. Both the lack of spectral shift with increasing solvent polarity and the reactivity towards hydrogen-atom donors indicate that 3NFA is an nπ* state which retains its nπ* character even in polar solvents.Item Adsorption of Methane + Ethane and Methane +Carbon Monoxide on Molecular Sieves(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1981, 77 (06), 1981) Veyssiere, Marie-Claude; Clavaud, Christian; Cartraud, Pierre; Cointot, AndreExperimental sorption isotherms are obtained for methane, ethane and carbon monoxide in three molecular sieves (two zeolitic and one carbon). Pressures from a few millibar absolute to as high as 30 bar are covered. Sorption isotherms for the binary mixtures methane + ethane and methane + carbon monoxide in the same sorbents are also obtained at 298 K and at equilibrium pressures within the range 2–12 bar. A circulating volumetric apparatus was built and employed for all the binary mixture sorption investigations. Total adsorbed amounts are determined for different gas-phase compositions. Vapour–adsorbate equilibria are determined. A correlation based on I.A.S.T. (Ideal Adsorbed Solution Theory) was studied in order to predict the vapour–adsorbate equilibria.Item Kinetic Studies of Photoinduced Methyl Viologen Reduction with Ruthenium Complexes and Hydrogen Evolution from Water by Hydrogenase(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1981, 77 (06), 1981) Okura, Ichiro; Kim-Thuan, NguyenHighly active photoinduced systems for methyl viologen reduction have been developed by using ruthenium complexes with long lifetimes in the photoexcited state. The order of activities is as follows: Ru(dime-phen)2+3 > Ru(Cl-phen)2+3 > Ru(phen)2+3 > Ru(bpy)2+3. By kinetic studies the rate constants for quenching the excited ruthenium complexes by methyl viologen have been determined. When hydrogenase was added to the systems containing ruthenium complex, methyl viologen and reducing agent, hydrogen evolution was observed in every system. A higher activity for hydrogen evolution was observed for the system having a higher activity for methyl viologen reduction.Item Study of Charge-transfer Interaction in Biomolecules(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1981, 77 (06), 1981) Lahiri, Jyotirmay; Basu, RamaThe interaction of the antibiotic drugs tetracycline and oxytetracycline with purines, pyrimidines and amino acids were studied spectrophotometrically in water, ethylene glycol and propylene glycol. In each case a new absorption band was located and denoted as a charge-transfer band. The formation constants for the charge-transfer complexes were determined using Benesi–Hildebrand's method followed by an iterative procedure. Different linear plots for hv against the highest filled π-molecular orbital of the donors (purines, pyrimidines and amino acids) were obtained indicating different stabilization energies for each system.Item Cooperative Interactions and Two-dimensional Ordering in the Adsorption of HBr on KBr(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1981, 77 (06), 1981) Harrison, Lionel G; Koga, Yoshikata; Lassau, TroyAdsorption isotherms of HBr gas on high surface area KBr have markedly non-ideal shapes. These are analysed using a two-layer model with repulsive interactions between molecules in the first layer. An earlier report from this laboratory of a transition in the surface layer at 20 °C, induced by adsorption, is confirmed by these data. Likewise, an apparent restriction of first-layer adsorption to no more than 25% coverage seems to correlate with the previous report from this laboratory that a ‘two-dimensional compound’ K4Br3Cl is formed in surfaces partly exchanged with HCl. Heat of adsorption is 48.5 kJ mol–1(below transition) and 30.5 kJ mol–1(above transition); mean-field repulsion constant C is ca. 40 kJ mol–1; the transition has ΔHt= 18.0 kJ mol–1 and ΔSt= 59.0 J mol–1 K–1. The remarkably large magnitudes of some of these quantities are discussed in terms of a model for adsorption involving normal weak hydrogen bonding plus additional electrostatic interactions between the Br of adsorbed HBr and adjacent K+ ions. Thereby, interactions between admolecules become intermediate-range, rather than nearest neighbour, averaging C/12 ≈ 3–4 kJ mol–1.Item Vapour-phase Exciplex Formation between 1,4-Dicyanonaphthalene and 2,5-Dimethyl-2,4-hexadiene(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1981, 77 (06), 1981) Abbott, Geoffrey D; O’CoNNOR, Desmond V; Phillips, DavidFluorescence has been observed from the exciplex formed between electronically excited 1,4-dicyanonaphthalene and 2,5-dimethyl-2,4-hexadiene in the vapour phase and the kinetics of exciplex formation studied. The enthalphy of vapour-phase exciplex formation in this pair of molecules was found to be 8 kJ mol–1 and activation energies for formation and reverse dissociation of the exciplex were found to be 15 and 23 kJ mol–1, respectively.Item Adsorption of Binary Gas Mixtures in Ion-exchanged Forms of Mordenite(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1981, 77 (06), 1981) Vansant, Etienne F; Voets, RafPure-component adsorption isotherms of CO, CO2, N2 and CH4 and multicomponent isotherms of CO + CO2, CO2+ N2 and CO2+ CH4 on mordenite were measured at 273, 258 and 243 K. No evidence of enhanced sorption of one component over the other was found. Adsorption of gas mixtures on different exchanged mordenites reveals that the separation ability increases with increasing electrostatic field in the adsorption cavities. The effect of the nature of the entering gas molecules on the separation is explained by the cationic and non-cationic specific character of the adsorption process. The temperature sensitivity and selectivity of the individual components influence the extent of the competition so that the separation increases significantly with decreasing adsorption temperature. The highest separation of gas mixtures into their pure components was observed at low adsorption temperatures, low percentages of CO2 in the residual gas phase and at high total equilibrium pressures.Item Theory of Compartmentalised Free-radical Polymerisation Reactions Part 5(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1981, 77 (06), 1981) Birtwistle, David T; Blackley, David CAn iterative procedure has been developed for the numerical solution of the exact Smith–Ewart differential difference equations for a compartmentalised free-radical polymerisation reaction in the non-steady state. The procedure is of wide applicability, being capable of extension to include states of as high a radical-occupancy as is considered to be appropriate to the reaction system under consideration. The procedure is also in principle capable of application to reaction systems whose characterising parameters are time-dependent. Examples are given of results obtained using the procedure, and comparisons are made with the corresponding predictions of the Poissonian approximation described in a previous paper in this series.Item Solute Interactions in Dilute Aqueous Solutions Part 4.—Microcalorimetric Study of Ternary Mixtures of Urea and Hydrophobic Species(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1981, 77 (06), 1981) Franks, Felix; Pedley, Michael DHeats of dilution of urea, acetone, ethylmethyl ketone and tetrahydrofuran, and heats of mixing of urea with each of the other solutes have been measured at 25°C; the urea + acetone system was also studied at 5°C. The various enthalpic pair and triplet interaction coefficents, hij, hijj, etc. have been evaluated. The hii for the ketones and THF are positive and show a dependence on the alkyl chain length typical of the hydrophobic pair interaction, while for urea hii is negative. The cross coefficients hij are small, but positive. The triplet coefficients are generally small and of variable sign. At 5°C, all the coefficients are of a greater magnitude. The results are discussed in terms of various models for aqueous solutions of urea.