Kinetics and mechanism of reduction of thallium(III) by hydrogen peroxide in perchloric acid medium

The kinetics and mechanism of reduction of thallium(III) by hydrogen peroxide has been studied in 1.0 mol dm^–3 perchloric acid medium. The reaction is first order with respect to thallium(III) and second order with respect to hydrogen peroxide. A negative hydrogen ion and chloride ion catalysis is observed. Bromide ion is found to catalyze the reaction in low concentration. There is no effect of ionic strength on the rate of the reaction. A plausible mechanistic pathway for the reaction is suggested which leads to the following rate law: Rate=–d[T1(III)]/dt=kK[T1(III)][H₂O₂]²/[H⁺] where K is the formation constant of the complex between thallium(III) and hydrogen peroxide and k is the rate constant of the reaction between that complex and hydrogen peroxide. The computed values of E_a and S^# are 44.8±6.5 kJ mol^–1 and –107.8±22.2 JK^–1 mol^–1, respectively.

---

(III) - - . - (III) . - - . . -- . , - :=–[T1(III)]/dt=kK[T1(III)][H₂O₂]²/[H⁺], - (III) - . E_A S^# 44,8±6,5 / –107,8±22,1 /·, .

     

Combinations of alkyl radicals with alkyl and substituted allyl radicals

In contrast with expectations based upon simple collision theory, reactions of alkyl radicals with substituted allyl radicals yield cross-combination ratios of =2. Reactions of CH ₃ ^\ with some C₅ radicals give >2, in accordance with theory.

---

, =2. CH₃ ^\ C₅ >2, .

     

Deuteration effect in auto-oscillation chemiluminescence of the Belousov-Zhabotinskii reaction

It has been established that substitution of H₂O by D₂O in the auto-oscillation system of malonic acid+bromate+catalyst (Ce^{3+ 4+}, Ru(bipy) ₃ ^{2+, 3+} ) not only changes the parameters of oscillations recorded according to the chemiluminescence intensity, but can also lead to their complete disappearance. The step that is responsible for the D₂O effect on chemiluminescent oscillation reactions is the deuteration of the methylene group of malonic acid.

---

, H₂O D₂O — — (Ce^3+,4+, Mn^2+,3+, Ru(bipy) ₃ ^2+,3+ ) , , . , D₂O , .

     

Catalytic properties of silica-molybdenum catalysts in propylene oxidation

The activity of silica-molybdenum catalyts in propylene oxidation is shown to be determined by the partially dehydrated silica-molybdenum heteropolyacid stabilized by the SiO₂ surface.

---

, , SiO₂.

     

Catalytic decomposition of N2O on La2Cu0.5M0.5O4 (M=Co, Ni, Cu and Zn)

Decomposition of N₂O has been studied over La₂Cu_0.5M_0.5O₄ (M=Co, Ni, Cu and Zn) between 380 and 485°C at 50 torr initial pressure of N₂O to understand the mutual interaction of two different active metal ions of the same concentration and valence in deciding the physico-chemical and catalytic properties. A multicenter type of adsorption of N₂O has been visualized and it is found that the rate is governed by the electronic factor.

---

N₂O La₂Cu_0,5M_0,5O₄ (M=Co, Ni, Cu Zn) 380–485°C N₂O, 50 . , - . N₂O. .

     

The influence of basic calcium chloride nuclei on the hydration of calcium chloridesilicate

The influence of CaCl₂ · Ca(OH)₂ · H₂O nuclei on the hydration of Ca₃SiO₄Cl₂ was studied by means of calorimetry, X-ray diffraction, simultaneous DTA-TG and chemical analysis of the liquid phase.

---

Zusammenfassung Der Einfluss von CaCl₂ · Ca(OH)₂ · H₂O-Zusätzen auf die Hydratation von Calciumchlorid-silicat Ca₃SiO₄Cl₂ wurde durch Kalorimetrie, Röntgenbeugung, simultane TG-DTA und chemische Analyse der flüssigen Phase untersucht.

---

l₃ · ()₂ Ca₃SiO₄Cl₂ , .

     

Etude cinetique de la decomposition thermique de l'anhydride chromique depose sur alumine

Résumé On présente les résultats obtenus dans l'évaluation des paramètres cinétiques de la réaction de décomposition thermique de l'anhydride chromique déposé sur de l'alumine. Grâce aux données sur l'influence de la teneur en anhydride chromique et de la vitesse de chauffage sur les paramètres cinétiques, on obtient des conclusions sur les conditions d'obtention du catalyseur Cr₂O₃/Al₂O₃.

---

Results obtained in the determination of the kinetic parameters of the thermal decomposition of CrO₃ on alumina are presented. The experimental data on the effects of CrO₃ concentration and heating rate on the kinetic parameters are used to draw conclusions on the conditions of preparation of Cr₂O₃/Al₂O₃ catalysts.

---

Zusammenfassung Die bei der Bestimmung der kinetischen Parameter der thermischen Zersetzungsreaktion von CrO₃ auf Aluminiumoxid-Träger erhaltenen Ergebnisse werden erörtert. Aus den Versuchsangaben über den Einfluß der Cr₂O₃-Konzentration und die Aufheizgeschwindigkeit auf die kinetischen Parameter werden Schlüsse bezüglich der Herstellungsbedingungen der Cr₂O₃/Al₂O₃-Katalysatoren gezogen.

---

, Cr₃ . Cr₂O₃ , Cr₂O₃/l₂O₃.

     

Effect of deuteration on the thermal dehydration of lithium sulfate monohydrate

Effects of deuteration on the thermal stability, enthalpy change and kinetic parameters for the thermal dehydration of Li₂SO₄·H₂O were examined by means of TG and DSC. The enthalpy change for the monohydrate was smaller by 1.63±0.75 kJ/mol than that for the monodeuterate. The rate constant for the monohydrate was a little larger than that for the monodeuterate. However, the thermal stability, activation energy and frequency factor were practically unaffected by deuteration of the hydrate. It is suggested that the activation entropy as well as the activation energy should be considered in explaining the kinetic deuterium isotope effect in the thermal dehydration of Li₂SO₄·H₂O.

---

Zusammenfassung Die Wirkung der Deuterisierung auf die Thermostabilität, die Enthalpie-Änderungen und kinetischen Parameter der thermischen Dehydratisierung von Li₂SO₄·H₂O wurden durch TG und DSC untersucht. Die Enthalpie-Änderung für das Monohydrat wurde um 1.63±0.75 kJ/mol niedriger gefunden als für das Monodeuterat. Die Geschwindigkeitskonstante für das Monohydrat war etwas größer als für das Monodeuterat. Die Thermostabilität, die Aktivierungsenergie und der Frequenzfaktor wurden jedoch von der Deuterisierung des Hydrats praktisch nicht beeinflußt. Es wird vorgeschlagen, daß bei der Erklärung des kinetischen Deuterium-Isotop-Effekts bei der thermischen Dehydratisierung von Li₂SO₄·H₂O sowohl die Aktivierungsentropie als auch die Aktivierungsenergie berücksichtigt werden müssen.

---

, Li₂SO₄·H₂O. 1.63+0.75 /. , . , , . , Li₂SO₄·H₂O.

     

Catalytic activity of honeycomb catalysts, I. The benzene-cyclohexane (de)hydrogenation reaction

Monolithic supported platinum catalysts were investigated with respect to their hydrogenation and dehydrogenation activity towards benzene and cyclohexane, respectively, between 250° and 350°C. Conversion of benzene to cyclohexane is optimal for the volume ratio H₂/Bz=5 at lower temperatures. In the cyclohexane dehydrogenation reaction, high temperatures, associated with lower N₂/Cy ratios, are beneficial. No byproducts were observed in the two reactions.

---

, , 250 °C 350 °C. H₂/=5. N₂/ . .

     

Thermal Behaviour of some dioxane adducts ofM(C6F5)2 (M=Pd,Pt)

The thermal treatment of the pentafluorophenyl derivativesM(C₆F₅)₂Dx_n [M=Pd (n=2, 3) or Pt (n=2); Dx=dioxane] leads to the formation of the new dioxane adducts M(C₆F₅)₂Dx (M=Pd, Pt) and Pt(C₆F₅)₂Dx_1.5. Calculations of the order of reaction and the activation energy of some of the decomposition reactions are described. The values were determined by the Coats-Redfern and Freeman-Carroll methods. Structural data on the isolated intermediates were obtained by infrared spectroscopy and magnetic susceptibility measurements.

---

Zusammenfassung Die thermische Behandlung der PentafluorphenylderivateM(C₆F₅)₂Dx_n [M=Pd (n=2, 3) oder Pt (n=2); Dx=Dioxan] führt zu der Bildung der neuen DioxanaddukteM(C₆F₅)₂Dx (M=Pd, Pt) und Pt(C₆F₅)₂Dx_1.5. Die Berechnungen der Reaktionsordnung und der Aktivierungsenergie einiger Zersetzungsreaktionen werden beschrieben. Die Werte wurden durch die Methoden von Coats-Redfern und Freeman-Carroll bestimmt. Die Strukturangaben der isolierten Zwischenprodukte wurden durch Infrarotspektroskopie und Messung der magnetischen Suszeptibilität erhalten.

---

(₆F₅)₂, M=Pd n=2, 3 Pt _n=2, - , -M(C₆F₅)₂ (=Pd, Pt) (₆F₅)_21,5. , — —. .

     

Effect of homogeneous initiator on heterogeneous-homogeneous oxidation of methane

A kinetic method of freezing out free radicals combined with recording ESR spectra was used to study the HCl effect on the partial oxidation of methane over SiO₂. This effect is ascribed to the surface modification of catalyst.

---

HCl SiO₂. .

     

Kinetics of carbonyl triplet reactions in water

The presence of urea during the gelling of AlPO₄–Al₂O₃ catalysts (AlPO₄/Al₂O₃ weight ratio =3) has been studied with respect to its effect on the porous texture and surface acidity of the resulting gels. An increase in pore volume and mean pore radius with no modification in surface acidity is found when the AlPO₄–Al₂O₃ catalyst is modified by the addition of 5 mol% urea in the AlPO₄ solution.

---

, AlPO₄/Al₂O₃ ( AlPO₄/Al₂O₃=3) . , AlPO₄/Al₂O₃ 5 .% AlPO₄ - .

     

Experimental study of the initial stage of Li2SO4·H2O single crystal dehydration in vacuum

The initial stage of the Li₂SO₄·H₂O single crystal isothermal dehydration has been studied by means of quartz crystal microbalance. As found, weight loss in the initial process may be considered as H₂O molecule diffusion from a semiinfinite medium. The numerical values of the H₂O molecule diffusion in Li₂SO₄·H₂O have been calculated from the results obtained.

---

. - - - -. - Li₂SO₄·H₂O.

     

Effect of solvent on photochemically induced olefin metathesis by tungstenhexacarbonyl

Effect of solvents on photochemically induced metathesis of pentene-2 by W(CO)₆ has been investigated. Structure of the catalyst and a reaction mechanism are proposed.

---

-2 W(CO)₆. .

     

Kinetics of ion-exchange of transition metals on tin(IV) arseno-silicate cation exchanger

Exchange kinetics of some transition metal ions on tin(IV) arsenosilicate has been studied at various temperatures under particle diffusion controlled conditions. Various useful kinetic parameters such as self-diffusion coefficient (D_o), energy of activation (E_a) and entropy of activation (S^*) have been calculated and compared with other similar materials.

---

(IV) . , (D_O), (E_a) (S^*), .

     

Thermoanalytical investigation of ion exchange resins. The swelling water of anion exchange resins

The water uptakes of completely swollen and air dried anion exchange resins were investigated by traditional and also by thermoanalytical measurements. In investigations on the air dried resin samples of HSO₄, H₂PO₄, SO₄, HPO₄ and PO₄ forms, two types of water (strongly and loosely bound) were found. The sequence of water uptake on the resins investigated was compared to the opposite order of the adsorption strengths of the anions and to the entropies of the hydrated anions. A conclusion was made regarding the role of the hydration of the anions in the selectivity sequence of anion exchange.

---

Zusammenfassung Die Wasseraufnahme vollständig angequollener und lufttrockener Anionenaustauscherharze wurde mittels herkömmlicher sowie auch thermoanalytischer Messungen untersucht. Bei den Prüfungen der lufttrockenen Harzproben in den HSO₄-, H₂PO₄-, SO₄-, HPO₄-, und PO₄-Formen wurden zwei Arten von Wasser gefunden: stark und schwach gebundenes. Die Reihenfolge der Wasseraufnahme wurde mit der umgekehrten Reihenfolge der Adsorptionsstärke der Anionen und mit der Entropie der hydratisierten Anionen verglichen. Schlüsse bezüglich der Rolle der Hydratisierung der Anionen bei der Selektvititätsreihenfolge des Anionenaustausch wurden gezogen.

---

Résumé On a étudié par des mesures traditionnelles et par analyse thermique l'absorption d'eau par des résines échangeuses anioniques totalement gonflées et séchées à l'air. Lors de l'étude des échantillons de résines séchées à l'air, de formes HSO₄, H₂PO₄, SO₄, HPO₄ et PO₄, on a trouvé deux types d'eau: de l'eau fortement liée et de l'eau faiblement liée. On a comparé l'ordre de l'absorption d'eau des résines étudiées à l'ordre inverse des forces d'adsorption des anions et à l'entropie des anions hydratés. On en tire des conclusions sur le rôle de l'hydratation des anions sur la sélectivité de l'échange anionique.

---

- , . - HSO₄-, H₂PO₄-, SO₄-, HPO₄-, PO₄- : . . .

     

Oxidizing properties of alumina towards alcohols. Possible reaction scheme

By chemical trapping, an acyl species has been evidenced in the oxidation of alcohols to carboxylate on an alumina surface. A possible reacton scheme is discussed.

---

. .

     

NMR studies of the interaction between tris-acetylacetonates of Fe(III), Cr(III) and diethyldichloride of Sn (IV)

Paramagnetic relaxation rate of CH₂ protons has been found to be higher than that of CH₃ protons of SnEt₂Cl₂ in the presence of tris-acetylacetonate of Cr(III) in chloroform at 298 K, which supports the specific interactions between these compounds. The revealed ligand exchange between Cr(AA)₃, Fe(AA)₃ and SnEt₂Cl₂ takes place with the equilibrium shifted to the side of initial reactants.

---

, -CH₂ CH₃- SnEt₂Cl₂ - Cr(III) 298 K, . Cr(AA)₃, Fe(AA)₃ SnEt₂Cl₂, .