Showing papers on "Chemical decomposition published in 1983"
TL;DR: In this article, the authors discuss desorption and decomposition de NO adsorbe sur un catalyseur Rh/SiO 2, par spectroscopie de desorcisation a temperature programe.
Abstract: Etude de la desorption et de la decomposition de NO adsorbe sur un catalyseur Rh/SiO 2 , par spectroscopie de desorption a temperature programmee
75 citations
TL;DR: In this paper, it has been shown that iron(III, copper(II), and manganese(II) contaminants of alkali-metal hydroxides not only enhance the rate of hydrogen peroxide decomposition, but also result in the rate maximum being observed at a different pH value of 11.6, 12.0, and 9.5.
Abstract: It has been shown that iron(III), copper(II), and manganese(II), common contaminants of alkali-metal hydroxides, not only enhance the rate of alkali-induced decomposition of hydrogen peroxide, but also result in the rate maximum being observed at a different pH value of 11.6, 12.0, and 9.5, respectively. Different methods are recommended for the production of high-purity alkali solution and removal of contaminants. The addition of ethylenediaminetetra-acetic acid (H4edta) to the reaction mixture resulted in a further decrease in the decomposition rate and three stages could be distinguished in the rate vs. time curves. The lowest rate (stage II) is proportional to the square of the hydrogen peroxide concentration and to the hydroxide-ion concentration. During this stage, formation of hydroxyl and superoxide radicals was observed. It is believed that the true rate of the alkali-induced decomposition of hydrogen peroxide can be determined if purified alkali and chelating agent are simultaneously employed: the rate coefficient is 3 × 10–6 dm3 mol–1 s–1 at pH 11.6, 10–3 mol dm–3 H4edta, and 0.1 mol dm–3 H2O2 at 308 K.
66 citations
TL;DR: In this article, it was shown that thiohydroxamic esters in general decompose smoothly by a radical chain reaction to give carbon radicals which can be quenched in a synthetically useful manner.
47 citations
TL;DR: In this article, the progressive nature of the process of dehydration of Ca(NO3)2·4 H2O has been shown not due to consecutive decomposition reactions, as believed so far, but is the result of various physical processes, such as the incongruent melting of the material, the boiling and evaporation of the unsaturated or saturated solution formed, as well as the crust formation and drying of the surface of the solidifying residue.
Abstract: The progressive nature of the process of dehydration of Ca(NO3)2·4 H2O has been shown not to be due to consecutive decomposition reactions, as believed so far, but is the result of various physical processes, such as the incongruent melting of the material, the boiling and evaporation of the unsaturated or saturated solution formed, as well as the crust formation and drying of the surface of the solidifying residue. The quasi-isothermal-quasiisobaric thermogravimetric technique and the phase diagram of the Ca(NO3)2-H2O system were used to evaluate the results.
31 citations
27 citations
TL;DR: Decomposition en orthophosphite HPO 3 2−−. Energie d'activation as discussed by the authors, La vitesse augmente avec le pH de pH 3 a 7.
Abstract: Decomposition en orthophosphite HPO 3 2− . Energie d'activation. La vitesse augmente avec le pH de pH 3 a 7. Ni catalyse l'echange isotopique entre H 2 PO 2 - et D 2 O et la decomposition
27 citations
Patent•
05 Jul 1983TL;DR: In this paper, an oxygen generator is provided in the form of a housing having isolated first and second chambers, and a heat absorbing hydrated salt is also provided so as to be present during the reaction to absorb the excessive heat released upon the exothermic chemical decomposition of the oxygen-generating material.
Abstract: An oxygen generator is provided in the form of a housing having isolated first and second chambers. Oxygen-generating material is placed in the first chamber and a catalyst for activating the oxygen-generating material is placed in the second chamber. A heat-absorbing hydrated salt is also provided so as to be present during the reaction to absorb the excessive heat released upon the exothermic chemical decomposition of the oxygen-generating material. The salt has an endothermic dehydration reaction temperature below 50° C. A membrane is operationally connected to the reaction chamber to allow the generated oxygen to be expelled from the reaction chamber while retaining the material contents therein.
23 citations
TL;DR: In this paper, the main reaction channel of silance decomposition in glow discharges is the electron-impact-induced fragmentation into SiH2 radicals (or ions) and H2 molecules.
Abstract: The chemical relaxation technique consists of measuring the response of a chemical system to a small disturbance of an equilibrium or a nonequilibrium steady state. Since, for a small perturbation, the response of any complex and stable system is linear, rate constants of elementary processes under actual plasma conditions can be evaluated directly from the relaxation data. Applications of this technique to the kinetic study of the formation and decomposition of silane are presented and compared with previous data obtained by a flow method. In addition, relaxation data are presented which show that the main reaction channel of silance decomposition in glow discharges is the electron-impact-induced fragmentation into SiH2 radicals (or ions) and H2 molecules.
21 citations
TL;DR: In this paper, the existence of a symmetric bidentate bridging formate as stable intermediates in the decomposition of formic acid on the Ru(001) surface was demonstrated.
21 citations
TL;DR: In this article, the authors developed a method for complete decomposition of cation exchange resins with H2O2 in the presence of Fe3+ ion, and the decomposition reaction proceeded at ambient temperature and decomposition time was greatly shortened with increasing concentration of Fe 3+ ion rather than that of H 2O2.
Abstract: Ion exchange resins are widely used in the field of nuclear industry. The present work aimed at the development of a method for complete decomposition of cation exchange resins with H2O2 in the presence of Fe3+ ion. The decomposition reaction proceeded at ambient temperature and decomposition time was greatly shortened with increasing concentration of Fe3+ ion rather than that of H2O2. The catalytic action of Fe3+ ion was suppressed with increase of HNO3 concentration. As much as 4 g of the air-dried resin could be decomposed with 8 ml of 30% H2O2, and the use of about 60 ml of 30% H2O2 resulted in the complete decomposition of organic carbon to CO2. Absence of any orgnaic carbon in the residual solution will simplify the final disposal.
19 citations
TL;DR: The chemical equilibria representing the reactions were investigated by direct vapour pressure measurements and thermodynamic data such as free energies and enthalpies of reaction have been calcu....
Abstract: The chemical equilibria representing the reactionsandwere investigated by direct vapour pressure measurements and thermodynamic data such as free energies and enthalpies of reaction have been calcu...
TL;DR: In this article, it was shown that ethanol is firstly oxidized to acetaldehyde via a reaction initiated by nitric acid but carried on by NO2 radical, and the acetaldehyde is then oxidized by two independent paths leading one to acetic acid and the other to oxalic acid and eventually to CO2.
Abstract: The oxidation of ethanol as a model of the alcohols produced in the hydrolysis of nitrate esters, by nitric acid in aqueous sulphuric acid solutions has been studied with the aim to obtain information on the decomposition reaction of “spent acids”. The results show, in agreement with previous suggestions from this laboratory, that ethanol is firstly oxidized to acetaldehyde via a reaction initiated by nitric acid but carried on by NO2 radical. The latter is formed by the interaction of nitric and nitrous acids. The acetaldehyde is then oxidized by two independent paths leading one to acetic acid and the other to oxalic acid and eventually to CO2. The relevance of these findings on the understanding and on the control of „spent acids” is briefly discussed.
TL;DR: In this paper, the overall yield was degraded to 24 in good overall yield via 7, 10, 16, 21, 19 and 20 ; similarly, 24 was obtained from 2 and 3.
TL;DR: In this article, the reaction of formic acid (DCOOH) on Pt(111), Pt(1)-(2×2)S and Pt(3×√3)R30°S surfaces was examined by temperature programmed reaction spectroscopy.
TL;DR: The chromatographic behavior of xanthate complexes is seriously affected by decomposition effects as discussed by the authors, and separation of the xanthates without decomposition is possible if reversed phases, especially CN- or DIOL-modified reversed phases are used.
Abstract: The chromatographic behaviour of As(III), Sb(III), Bi(III), Se(II), Te(II) and Ni(II)xanthate complexes is seriously affected by decomposition effects. Polar stationary and mobile phases acting as Lewis bases cause decomposition of the complexes by displacing the xanthate ligands. Separation of the xanthate complexes without decomposition is possible if reversed phases, especially CN- or DIOL-modified reversed phases, are used.
TL;DR: In this article, the effect of catalyst properties such as surface area, non-stoichiometry and electrical characteristics on the thermal decomposition of KClO4 was investigated using thermogravimetric analysis.
TL;DR: In this paper, it has been shown that the presence of small concentrations of alkali or alkaline earth salts in the naturally occurring minerals has a strong effect on their decomposition and that the rate of decomposition is enhanced relative to pure dolomite when small amounts of chloride salts such as LiCl, NaCl, MgCl 2 and CaCl 2 are added.
TL;DR: In this article, six alkali metal nitrates and nitrites were evaporated in vacuum at a constant heating rate in a combined mass spectrometric and thermogravimetric apparatus.
Abstract: Six alkali metal nitrates and nitrites were evaporated in vacuum at a constant heating rate in a combined mass spectrometric and thermogravimetric apparatus. Time resolved profiles of decomposition gases and kinetics were obtained for LiNO3, NaNO3, KNO3, Na/KNO3, NaNO2 and KNO2. Activation energies for the evaporation of these salts were calculated and compared to previous results of isothermal experiments. In the temperature range 650–850 K, the decomposing nitrates released NO, N2 and O2 while the nitrites released only NO and N2.
Patent•
ARCO1
TL;DR: In this article, an improved process for oxidizing a hydrocarbon to produce a reaction mixture containing the corresponding organic hydroperoxide of said hydrocarbon and decomposing it to provide a mixture containing reaction products of said decomposition reaction, including alcohol and/or ketone products, in the presence of a catalytic quantity of a catalyst system comprised of ruthenium and chromium.
Abstract: There is disclosed an improved process for oxidizing a hydrocarbon to produce a reaction mixture containing the corresponding organic hydroperoxide of said hydrocarbon and decomposing said hydroperoxide to provide a mixture containing reaction products of said decomposition reaction, including alcohol and/or ketone products, comprising effecting said oxidation and/or decomposition in the presence of a catalytic quantity of a catalyst system comprised of ruthenium and chromium.
TL;DR: In this article, the thermal efficiency of the magnesium-iodine cycle for thermochemical hydrogen production has been evaluated based on material and energy balances for three proposed flow-sheets, and the three flowsheets varied according to the method used (quenching, selective absorption of HI by magnesium oxide and the two-step chemical decomposition of hydrogen iodide decomposition by magnetite) to separate the products of hydrogen ionization.
TL;DR: In this article, it was shown that the mechanism of calcite and calcite decomposition corresponds completely to reactions the total rate of which is limited by the decomposition at boundary of the phases, i.e. for which the condition f(α)=(1-α)n is valid.
TL;DR: In this paper, the rate constant k 1 of 1 was used to calculate k-3, the rate of decomposition of 4, and k 3/k 2 the rate ratio of the two possible modes of dimerisation of α-cyanoalkyl radicals.
Abstract: Ketenimines 4 are known to be formed in a side equilibrium during the thermal decomposition of azonitrile initiators 1, as e.g. 2,2′-azoisobutyronitrile (1a). The concentration of 4 was monitored by IR during the decomposition reaction of 1, and the final yield ratio of substituted succinonitrile 3 and nitrile 5 was determined by GC. Together with the rate constant k1 of 1, these data suffice for calculating k-3, the rate of decomposition of 4, and k3/k2 the rate ratio of the two possible modes of dimerisation of α-cyanoalkyl radicals 2.
TL;DR: In this article, the stabilization of the illuminated n-GaP electrode by Fe2+ ions is interpreted on the basis of a model in which the stabilization reaction is assumed to occur by electron transfer from the Fe2 ion to a surface intermediate of the anodic decomposition reaction of the semiconductor, whereas surface recombination is involved in ordinary surface states as well as decomposition intermediates.
Abstract: Experimental results on the stabilization of the illuminated n-GaP electrode by Fe2+ ions are interpreted on the basis of a model in which the stabilization reaction is assumed to occur by electron transfer from the Fe2+ ion to a surface intermediate of the anodic decomposition reaction of the semiconductor, whereas surface recombination is assumed to involve ordinary surface states as well as decomposition intermediates. The numerical treatment of the ensuing kinetic equations leads to results which are in good agreement with the experimental data.
TL;DR: Stabilite et cinetique de dissociation et de formation du complexe d'Ag de la monensine dans plusieurs solvants (methanol, DMF, acetonitrile, DMSO) as mentioned in this paper.
Abstract: Stabilite et cinetique de dissociation et de formation du complexe d'Ag de la monensine dans plusieurs solvants (methanol, DMF, acetonitrile, DMSO). Les vitesses de formation sont pratiquement controlees par la diffusion
TL;DR: A theory of electron transfer between adsorbed ions and electrically charged ionic surfaces is developed in this paper, where electron transfer from a charged AgBr surface to an Ag + ion, as well as from Br − ion to AgBr surfaces holes are studied.
TL;DR: In this article, the first-order rate constant for the formation of acetaldelyde from alanine under these conditions is k4 = 1.98 × 1015e−22,500/RT min−1.
Abstract: Aqueous bromine reacts with alkyl-sidechain amino acids through a series of steps resulting in the formation of the corresponding alkyl aldelydes and nitriles. The kinetics and the mechanism of the interaction of bromine with alanine are examined. The products and the rates of this reaction are dependent in a complex way on the initial reactant concentration and pH. Acetaldeyde production is favored at low bromine-to-alanine ratios, low bromine concentrations, and pH values above 6. The first-order rate constant for the formation of acetaldelyde from alanine under these conditions is k4 = 1.98 × 1015e−22,500/RT min−1. At higher concentration the nitrile is formed through a bromoimine intermediate. Under most conditions the nitrile appears to form from a catalyzed decomposition of the bromoimine which is too fast to be followed by the methods used in this study. However, residual amounts of the bromoimine decay by a slower first-order mechanism. The rate constant for this slower reaction in the case of alanine at pH 6.8–6.9 and alanine concentrations of 1 × 10−4M is k6 = 1.75 × 105e−10,400/RT min−1.
TL;DR: In this article, the decomposition rates and equilibria of activated sulfones are determined by pH-stat titrations of the sulfinic acids liberated during decomposition reactions, which are correlated with the Hammett σ constants.
Abstract: Durch pH-Stat-Titration der beim Zerfall aktivierter Sulfone freigesetzten Sulfinsauren werden Reaktionsgeschwindigkeiten und Lage der Gleichgewichte ermittelt. Diese Werte lassen sich mit den σ-Hammett-Parametern korrelieren.
Kinetic Studies on Activated Sulfones
The decomposition rates and equilibria of activated sulfones are determined by pH-stat titrations of the sulfinic acids liberated during the decomposition reactions. The kinetic data are correlated with the Hammett σ constants.
TL;DR: In this article, the De Boer's t plot was applied on α-Fe2O3 produced from decomposition in vacuo and treated with water vapor at 532 Pa and at 200°C.
Journal Article•
TL;DR: Support for the above proposed chemical activation pathway was provided by correlations between in vitro cytotoxicity, in vivo antineoplastic activity, chemical stability, and the degree of alkylation of NBP by a wide variety of arylsulfonyl-hydrazones.
Abstract: The arylsulfonylhydrazones of 2-pyridinecarboxaldehyde 1-oxide represent a relatively new class of antineoplastic agents with the potential for clinical usefulness. The requirement for spontaneous chemical transformation of these agents to exert anticancer activity was evaluated using as the prototype the most potent member of this class synthesized to date, the 3,4-dimethoxybenzene sulfonylhydrazone of 2-pyridinecarboxaldehyde 1-oxide (3,4-DSP). 3,4-DSP was chemically unstable, decomposing with a half-life of 19 min in 0.01 m potassium phosphate buffer (pH 7.4) at 37°. The major chemical decomposition product was identified as 2-pyridylcarbinol 1-oxide by comparison with the authentic compound. This carbinol is hypothesized to be formed via the intramolecular abstraction of hydrogen from the arylsulfonylhydrazone, a process that leads to the release of 3,4-dimethoxybenzenesulfinic acid and the formation of 1-oxidopyridin-2-yldiazomethane, which subsequently reacts with water. The diazomethane intermediate is a potent alkylating agent which, if generated in cells, would have the potential to alkylate nucleophilic groups of biologically important macromolecules. The proposed reactive species was trapped using both 4-(4-nitrobenzyl)pyridine (NBP) and morpholine, and the latter product was characterized by mass spectroscopy. The importance of the chemical formation of an alkylating species to cytotoxicity was demonstrated by studies in which solutions of 3,4-DSP were “aged” prior to addition to L1210 leukemia cells in culture and prior to incubation with NBP. The “aging” of 3,4-DSP for 20 min resulted in a 4-fold decrease in cytotoxicity, and aging for 1 to 3 hr led to complete loss of cytotoxicity. Correspondingly, a 20-min aging period decreased alkylation of NBP by 51%, and 3-hr aging resulted in essentially no alkylation of the nucleophile. Further support for the above proposed chemical activation pathway was provided by correlations between in vitro cytotoxicity, in vivo antineoplastic activity, chemical stability, and the degree of alkylation of NBP by a wide variety of arylsulfonylhydrazones. The lack of the 1-oxide, envisioned to be required for intramolecular hydrogen abstraction, the steric prevention of the abstraction, or the replacement of the proton of the nitrogen of the side-chain by a methyl group resulted in a marked increase in chemical stability and a corresponding loss of the ability to alkylate NBP and to inhibit the replication of L1210 leukemia cells in culture.