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Item Adsorption and Oxidation of Dimethylaniline by Laponite(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1977, 73 (11), 1977) Vansant, Etienne F; Yariv, ShmuelColoration of synthetic Laponite by dimethylaniline was studied in relation to the adsorption data, and to different reaction conditions including the nature of the exchangeable cations, the pH and the concentration. Using visible and i.r. spectra, together with X-ray patterns, the colour reaction mechanism was investigated. The coloration could be ascribed to the following stages: (1) sorption of dimethyl-aniline, (2) oxidation by atmospheric oxygen into N,N-dimethyl-N′-methylbenzidine and bis-p(N,N-dimethylaminophenyl)-p(N′-methylaminophenyl)methane and (3) further oxidation to a blue quinoid cation or its protonated yellow component and to methyl violet, respectively.Item Oxidation of 1-Phenylethanol in the Presence of Cobalt Acetylacetonates(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1977, 73 (10), 1977) Vasvari, Gabor; Gal, DezsoThe oxidation of 1-phenylethanol has been investigated in the presence of Co(acac)2 and Co(acac)3. It is established that in the presence of Co(acac)2 the oxidation is preceded by the formation of a Co(acac)2—ROH complex and the fast oxidation stops abruptly due to the deactivation of the catalyst. The rate constants and the overall activation energy were determined. In the presence of Co(acac)3 the oxidation began after an induction period. It is assumed that the actual catalyst for this process is Co(acac)2. The overall activation energy has been determined.Item Oxidation of Formaldehyde in KCl-coated Vessels(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (07), 1974) Baldwin, Roy R.; Fuller, Alan R.; Longthorn, David; Walker, Raymond W.In the temperature range 440-540’C, the oxidation of HCHO in KCl-coated vessels is reproducible and of short chain length for HCHO concentrations in the range 0.05-4 Torr. Interpretation of the [CO] against time profile permits evaluation of the unknown parameters A'i, k7jk^ and ka. HCHO + O2->HO2 + HCO HO2 + HO2->H2O2 + O2 surface HO2---->4H2O + JO2 surface H2o2—>H2O + 4O2. (1) (4) (7) (8) Comparison of the experimental values for k7/kf and ka with those calculated from diffusion theory indicates that the destruction of HO2 at the surface is fully diffusion controlled, whereas the destruc tion of H2O2, though moderately efficient, is not fully diffusion controlled. From measurements at HCHO concentrations below 0.5 Torr, where the chain length is close to unity, effectively direct measurements of ki have been obtained, the values being 7.65 x 10~’, 2.08 x 10-1, 8.50 x IO-2 and 2.20x 1CF2 dm3 moF* s_1 at 542.5, 500, 471 and 440.5°C, respectively. These values give the Arrhenius parameters At = 2.04x 1010 dm3 moF1 s~l, £\ = 38.9 ± 1.5 kcal moF1. The absence of any diameter effect on the value of k, confirms that the parameters refer to the homogeneous pro cess.Item Kinetics of the Chlorine-Photosensitized Oxidation of Hydrogen at 1 Atmosphere Pressure, 306 K(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1977, 73 (2), 1977) Cox, Richard A.; Derwent, Richard G.The chlorine-photosensitized oxidation of hydrogen has been studied at 1 atmosphere total pressure and 306 K in a stopped-flow system. Hydrogen peroxide is the main oxidation product and its formation kinetics at high hydrogen concentrations are consistent with the following simple reaction scheme involving Cl, H and HO2: Cl2+hv→Cl + Cl, Cl + H2→HCl + H, H + O2+ M→HO2+ M, HO2+ HO2→H2O2+ O2. At lower hydrogen concentrations, a marked inhibition in the H2O2 production and Cl2 decay rates was observed, due to the reactions (5b) and (6), Cl + ClOO→Cl2+ O2, Cl + HO2→HCl + O2. (6) Computer analysis of the experimental data gave k5b=(2–1+2)× 10–11 and k6=(2.5 ± 1)× 10–11 cm3 molecule–1 s–1 at 306 K, 1 atmosphere pressure.Item Sequence Studies in Liquid Phase Hydrocarbon Oxidation Part 4: Hydroperoxide-Alcohol and Hydroperoxide-Ketone Transitions in the Oxidation of Ethylbenzene(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1977, 73 (1), 1977) Danoczy, Eva; Nemes, Istvan; Gal, DezsoThe rates of consumption of a-phcnylcthyihydroperoxide molecules during the oxidation of ethylbenzene at 120°C have been measured using radioactive tracer procedures; balance equations for the total activities and concentrations were used for the calculations. In order to obtain a coherent set of rates a hydrogen transfer reaction between hydroperoxide molecules and peroxy radicals had to be taken into account. It was established that ketone and alcohol molecules were formed mainly as a result of the induced decomposition of the hydroperoxide and the contribution to their formation by termination processes was <10 % of their total formation rates. The formation rates of alcohol and ketone via hydroperoxide molecules were very similar. The relative reactivity of hydroperoxide and ethylbenzene molecules toward peroxy radicals was found to be two. Further kinetic data, such as ease of oxidation and kinetic chain length both for the oxidation of the parent hydrocarbon and its main intermediate, have been determined.Item Compensation Effect in the Kinetics of the Catalysed Oxidation of Carbon(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (11), 1974) Feates, Frank S.; Harris, Peter S.A pattern of behaviour amongst catalysts in the catalysed oxidation of carbons has been identified. A link between the rates of the catalysed and uncatalysed reactions in these systems has been established. A phenomenological model has been developed which combines the principal results of bulk oxidation of heavily impregnated carbons and of electron microscopy experiments and which unites a large body of data under one interpretative umbrella.Item Low Temperature Gas-phase Oxidation of Aldehydes: Part 2.—Retardation by Formaldehyde above 120°C(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (1-6), 1974) Dixon, David J.; Skirrow, Geoffrey; Tipper, Charles F. H.The effect of added formaldehyde on the oxidation of acetaldehyde and propionaldehyde between 119 and 188°C has been studied using a static system. Formaldehyde retards the oxidation, and at 188°C the rate after 25 % consumption of CH3CHO(ρ0.25) is linearly related to the reciprocal of the initial concentration of CH2O(Fi). However, at 119°C ρ0.25 decreases to a minimum and then increases as Fi is increased. The change in formaldehyde concentration during retarded oxidations showed that CH3CHO and CH2O are both removed mainly by reaction with peracetyl radicals, CH3CO3+ CH3CHO→CH3CO3H + CH3CO (3), CH3CO3+ HCHO→CH3CO3H + HCO (7)k7/k3 being about 2.4 at 119 and 188°C. Only about one in seven of the formyl radicals give carbon monoxide at 119°C. The kinetic and analytical data are explained on the basis of the mechanism given in Part 1 with the addition of reaction (7). It is suggested that some performic acid is formed at 119°C and causes extra branching by reaction with acetaldehyde.Item Low Temperature Gas-phase Oxidation of Aldehydes: Part 1.—The Reaction Below 120°C(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (1-6), 1974) Dixon, David J.; Skirrow, Geoffrey; Tipper, Charles F. H.The gas-phase oxidation of acetaldehyde, propionaldehyde and the butyraldehydes, in an unpacked and a packed vessel between 45 and 120°C, has been studied using a static system with a very small dead volume. Contrary to earlier reports, below 70–80°C with very high aldehyde/oxygen ratios the final pressure decreases were not greater than, but agreed very closely with, the overall stoichiometry RCHO + O2→RCO3H. The variation of pressure with time agreed with that deduced from the usual autocatalytic chain mechanism 2 and confirmed, in particular, that the initiation process is first order with respect to both aldehyde and oxygen, that the addition of oxygen to CH3CO radicals is second order and that the branching process is first order with respect to both peracid and aldehyde. The variation of the second order rate coefficients with temperature and surface/volume ratio indicated that both initiation and branching are heterogeneous. However, the addition process is homogeneous, the rate coefficient being about 1.2 × 107 dm3 mol–1 s–1 between 62.5 and 83.5°C. Analyses of the minor products (CO, CO2, H2O, CH4, C2H6, CH2O, CH3OH, CH3COCH3, CH3COCOCH3) of the acetaldehyde oxidation and of the peracetic acid/acetaldehyde interaction after the oxygen was used up has given information on the chemical nature of the elementary steps occurring in initiation and branching.Item Oxidation of a Pyrophoric Iron: Part 2. Direct Measurement of Self-heating Accompanying Chemisorption of Oxygen on the Finely Divided Iron-Carbon Substrate(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (1-6), 1974) Galwey, Andrew K.; Gray, PeterThe self-heating accompanying the exposure to oxygen of a pyrophoric iron (here a finely divided iron-carbon preparation from an iron mellitate) has been studied quantitatively. In particular, temperature histories have been measured directly by means of a fine thermocouple located at the reactant centre. The dependence of the course of events on (i) initial temperature, from 193 to 720 K, (ii) oxygen pressure, from ca. 0.5 to 200 Torr and (iii) sample mass, from 16 to 40 mg has been investigated. Particular attention has been directed toward attaining really satisfactory reproducibility. All the phenomena observed correspond to sub-critical behaviour; ignitions have not been studied. The results are interpreted against the background knowledge (Part 1) of the kinetics of oxygen adsorption on this pyrophoric iron preparation. From the observations it is concluded that below 373 K and 4 Torr oxygen pressure, the extent of self-heating is determined by the rate of heat loss through the walls of the glass containing vessel. Above 4 Torr, the behaviour is more complex and is influenced by the occurrence of two distinct chemisorption reactions. Reaction above 500 K seems to be governed by gas diffusion processes and the overall temperature rise is moderated both by the containing vessel and by the diffusion of oxygen by inter- and intra-crystalline paths to the active surfaces within the particles of the reactant assemblage.Item Kinetics of the Oxidation of Isopropanol by Aquocobalt (III) Ions in Aqueous Perchlorate Media(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1973, 69 (3), 1973) R., Varadarajan; C. F., WellsThe kinetics of the oxidation of isopropanol by CoIIIaq have been studied using conventional and stopped-flow spectrophotometry in aqueous perchlorate media at high values for the ratio (initial [isopropanol])/(initial[CoIIIaq]) where Δ[CoIIIaq]/Δ[acetone]= 2.0. The rate is first order in [CoIIIaq] and first order in [isopropanol], and there is no evidence for intermediate complexes at very high [isopropanol]. The variation of the observed second order rate constant with acidity fits a mechanism where both CoIIIaq and CoIIIOH–aq react with the unprotonated alcohol, and energies E and entropies ΔS* of activation are compared with E and ΔS* for the oxidation of isopropanol by other cations and for the oxidation of other substrates by CoIIIaq in aqueous perchlorate media. The published data for the rates of oxidation of other alcohols by CoIIIaq conform to a mechanism similar to that for isopropanol, and the rate constants for various substrates with a range of oxidants are compared.