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Item Kinetics and Mechanism of the Quatemization of Poly(4-vinyl pyridine) with Ethyl, n-Propyl, n-Butyl, n-Hexyl and Benzyl Bromide in Sulpholane(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1977, 73 (10), 1977) Boucher, Ernest A.; Groves, John A.; Mollett, Christopher C.; Fletcher, Peter W.Kinetic results for quaternization reactions of four n-alkyl bromides (C2, C3, C4, C6) and benzyl bromide, with poly(4-vinyl pyridine) in sulpholane, at a variety of concentrations and temperatures, have been analysed according to a neighbouring-group model. A particular system is characterized by the rate constants ki for reaction of a pyridyl group having i= 0, 1 or 2 already reacted neighbours. Values of k0 under comparable conditions are given. The ratios K=k1/k0 and L=k2/k0 for the series of reagents: C2(0.95, 0.54), C3(0.80, 0.37), C4(0.70, 0.31), C6(0.55, 0.27) and Bz(0.75, 0.34), indicate that retardation as reaction proceeds, in excess of that expected from second-order kinetics, is due predominantly to steric (rather than electrostatic) effects. All of the results for the time dependence of extent, ξ, of reaction are corrected on the supposition that 5 % of the polymer consists of unreactive impurity; previous studies have shown evidence of impurities, but these have not been allowed for in the few attempts at kinetic analysis. Activation energies E0 are fairly constant for C2 to C6: 68.8 ± 3.3, 66.2 ± 4.3, 65.8 ± 4.0 and 66.0 ± 3.5 kJ mol–1; cf. 52.6 ± 4.9 kJ mol–1 for benzyl bromide. The k1 and the k2 show the same temperature dependence, within experimental error, as the k0, i.e.E0=E1=E2.Item Kinetics of Adsorption on Energetically Heterogeneous Surfaces(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1977, 73 (09), 1977) Crickmore, Peter J.; Wojciechowski, Bohdan W.Rate models for adsorption and desorption on a non-uniform surface are derived using the “ Extent of Reaction Effect ” which describes the behaviour of large systems of parallel reactions. When the rate models and the resulting isotherm are fitted to data taken from the literature, very good agreement is found between the fitted model and the data. The new isotherm also provides an explanation for cases where physisorption is observed to follow Langmuir’s dissociative chemisorption isotherm. Extensions of our rate model are presented for the case where a precursor state exists. This approach leads to two well-established isotherms: the Freundlich isotherm and the “ generalized Freundlich ” isotherm proposed by Sips.Item Kinetics of Quaternization of 4-Methyl and 4-Ethyl Pyridine with n-Propyl and n-Butyl Bromide in Sulpholane(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (02), 1978) Boucher, Ernest A.; Khosravi-Babadi, Ezatollah; Mollett, Christopher C.Kinetic measurements have been carried out in sulpholane to provide a basis for comparison with quaternization reactions of poly(4-vinyl pyridine), and to clarify the roles of steric and inductive effects. Activation energies, and rate constants at 319.2 K, taken from Arrhenius plots of about ten points for each reaction are: (A) 4-mcthyl pyridine+n-propyl bromide E/kJ mol-1 = 66.0 + 1.1, 105A/(dm3 mol-1 s~‘) = 8.21 ; (B) 4-ethyl pyridine+n-propyl bromide 63.3 + 2.2, 8.70; (D) 4- methyl pyridine+n-butyl bromide 65.0 + 0.7, 7.10; (E) 4-ethyl pyridine+n-butyl bromide 63.0± 1.5, 7.71. Concentrations of base and reagent were nominally 0.2 and 0.6 mol dm-3. The ethyl pyridine has a A'-valuc slightly greater than that for the methyl pyridine, and k for propyl bromide is 10-15 % greater than that for butyl bromide. The ratios A(A)/A(B) = 0.94 and A(D)/A(E) = 0.92 are remarkably constant. Reactions (C) and (F) for n-propyl bromide and n-butyl bromide and poly(4- vinyl pyridine), reported previously, give the ratios A(C)/A(A) = 0.80, A(C)/A(B) = 0.75, A.(F)/A(D) = 0.81, A(F)/A(E) = 0.74. A linear dependence of In A on (e—l)/(2e+l) was found for system (B) where e is the dielectric constant, which depends on the concentrations of reactants.Item Environmental Control of Reactions: Influence of Poly(L-glutamate) on the Kinetics of Decomposition of Hydrogen Peroxide Catalysed by Quaterpyridineiron (m) Complex Ions(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (02), 1978) Barteri, Mario; Farinella, Marcello; Pispisa, Basilio; Splendorini, LucianoThe decomposition of hydrogen peroxide catalysed by quatcrpyridineiron(ni) complex ions has been studied within the pH range 6.5-8. The reaction obeys total third-order kinetics with a partial order of two with respect to the substrate. At pH Rs 7.6, where the reaction velocity exhibits a maximum asymptotic value, the apparent activation energy is 29.3±2.9 kJ mol-1. Addition of poly (L-glutamate) (PLG) in solution determines a change in the overall kinetics. In this case, the process follows a total second-order equation and has an apparent activation energy of 53.1 ±6.3 kJ moly . At a fixed concentration of complex, saturation phenomena are observed in all cases on increasing the concentration of substrate. As expected, the Lineweaver-Burk plot of the polymer- free complex-catalysed reaction is nonlinear, whereas it is linear when the complex + PLG system is us5.d', At 25°C, the rate constant for the irreversible decomposition of the Michealis “ complex ”, which represents the rate-determining step, is k3 = 4.9 ±0.2 and 2.7 ± 0.2 s-1 for [Fe(tctpy) X2]nF and 1 c(. etpy)X2]"++PLG catalytic systems, respectively. Implications of the role played by the poly- pep ice matrix as environmental controller of the catalysis under study are briefly discussed.Item Kinetics of the Decomposition and Hydrogen Reduction of Nitric Oxide on Niobium, Nickel and Platinum Filaments at High Temperatures and Low Pressures(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (1), 1978) Morgan, John A.; Robertson, Andrew J. B.NO decomposition kinetics were studied with ultra-high vacuum techniques on niobium, nickel and platinum wire filaments at high temperatures with pressures between —1 and 100 m-2. Niobium readily decomposed NO with first-order kinetics, nitrogen and oxygen being deposited on the surface, resulting in a progressive loss of filament activity. Nitrogen was desorbed from nickel, which otherwise behaved similarly to niobium. Excess H2 affected the kinetics of NO reaction on these metals mainly by reaction with and subsequent removal of surface contaminants rather than by a direct reaction with NO. Platinum did not observably decompose NO at low pressures except in the presence of excess H2. Above ~1300 K the rate appeared to be determined by H2 atomisation, but at lower temperatures a reaction between H2 and NO may have been occurring. The rate-limiting step for this reaction may be the decomposition of H2 and addition of H atoms to adsorbed NO. The pre-exponential term for this reaction indicated that the transition state was mobile on the surface.Item Kinetics of Gas Phase Ion-Ion Recombination in NO++X- ->NO+X for X being Chlorine, Bromine and Iodine(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (1), 1978) Burdett, Nigel A.; Hayhurst, Allan N.The rate coefficient for the gas phase recombination of N0+ with halide ions X- in NO++X-->NO+X has been measured in flames of C2H2 + O2 + N2 over the temperature range 2200 to 2650 K. Chlorine, bromine and iodine have been used as X. All At values are in the range 0.8-2.lx 10~8 ion -1 cm3 s-1, corresponding to cross-sections (tto2) of ~10-17 m2. For each halogen, ki has a negative temperature coefficient. Also at any one temperature, kt is largest for X being chlorine and smallest for iodine. In general, these measurements are in agreement with Olson’s “ absorbing sphere ” model for ion-ion recombination.Item Kinetics of Gas Phase Electron—Ion Recombination by NO++e -> N-rO from Measurements in Flames(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (1), 1978) Burdett, Nigel A.; Hayhurst, Allan N.Mass spectrometric measurements of ion concentrations in the burnt gases of flames of either C2H2 + O2+N2 + occasionally trace amounts of NO or H2 + O2 + N2 with small additions of C2H2 and NO have enabled the rate coefficient, kit for electron-ion recombination in reaction (I) NO++e-->N+O (I) to be determined. Such measurements have been made for a wide variety of flame conditions over the temperature range 1820 to 2650 K and indicate that changes from 2.3xl0~7 to 1.4x 10-' ion-1 cm3 s~‘. At the lower temperatures kt varies as T-0’7, but as T~l's at the hotter ones. There is evidence that circumstances can be devised in flames, when charged species are produced by chemi-ionization in the reverse of reaction (I), whose rate coefficient is found to be 6.7 x 10'12 exp (-31 900/T) atom-1 cm3 s"1 from 1820 to 2650 K.Item Kinetics of Anionic Polymerization of Styrene in Binary Mixtures of Dimethoxyethane and Benzene(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (07), 1974) Takaya, K.; Yamauchi, S.; Ise, NorioThe kinetics of anionic polymerization of polystyryl salts with various gegen ions have been investigated spcctrophotomctrically in 1,2-dimethoxyethanc (DME) + benzenc mixtures at 25QC. The behaviour of two types of polymers, viz. one- and two-ended polymers, was studied for sodium and caesium salts. The two-ended sodium salt is as reactive as the one-ended salt, whereas the two- ended caesium salt is less reactive than the one-ended salt. The conductance of the two-ended sodium salt is smaller than that of the one-ended, whereas the conductance of the two-ended caesium salt is larger than that of the one-ended salt. The ion-pair rate constants k'p in the DME +benzene (50 : 50) mixture are 360, 182 and 90 dm3 mol-1 s-1 for the sodium, potassium and caesium salts. The dissociation constants K are 4.7 x IO-10, 1.3 x 1O~10 and 3.5 x IO-13 mol dm-3 for the sodium, potassium and caesium salts. The free ion rate constant kp is 9-10 x 104 dm3 mol-1 s"' for these salts. The contribution of the intra-molecular triple-ion was observed for the two-ended living polystyrene and the rate constant fcp'(c) of this ionic species is ~1000dm3 mol-1 s-1, practically independent of solvent, and; is smaller than the rate constant of the solvent-separated intcrmolccular triple ion (Ap'~1.2x 10s dm3 mol-1 s-1).Item Kinetics of Electrode Reactions in Liquid Ammonia: Part 4.—The Cun/Cu'/Cu° System in Acid Solution(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (07), 1974) Brown, Oliver R.; Thornton, Sean A.The Cu^/Cu1 redox system is fully reversible on gold or platinum electrodes and quasi-reversible on vitreous carbon. When the metal electrodes are anodically oxidised prior to the measurements, the redox process is inhibited and curvature in the polarisation data indicate that the electrodes behave as p-type semi-conductors. The system Cui/Cu° possesses unusual features. Whereas the dissolu tion of Cu° to Cu1 is quasi reversible (Xr0 = 8xl0-5cms-1) the deposition reaction is severely inhibited by the formation of unidentified insulating films which also retard the reduction of Cu11 to Cu1. This result explains the poor quality of electrodeposits of copper from ammonia solutions described in the older literature.Item Kinetics of the Thermal Gas-phase Decomposition of 6-Oxabicyclo[3,1,0]hexane(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (1-6), 1974) Flowers, Michael C.; Penny, David E.The kinetics of the gas-phase decomposition of 6-oxabicyclo[3,l,0jhcxanc have been studied over the temperature range 670-742 K. at pressures between 1 and 28 Torr. Isomerization to cyclopcnta- nonc and cyclopcnt-2-en-l-ol accounts for —97 of the primary reaction products and occurs by tirst-ordcr, homogeneous, non-radical processes. A'cyclopcntanonc/s-1 = 1014'10 + 11 cxp(-240 400 + 1500/8.314T) A-cyelorcnt^-en-i-ol/s-1 = 10‘3-5" T°-1" cxpf-242 200 + 2200/8.314T)