Structural and thermal analysis of phosphoramidothioate,phosphorodiamidothioate and N,N′-diphenylphosphorodiamidothioate complexes of Zn(II), Cd(II) and Hg(II)

A new series of complexes of Zn(II), Cd(II) and Hg(II) with phosphoramidothioate (PAT), phosphorodiamidothioate (PDAT) and N,N-diphenylphosphorodiamidothioate (N,N-DPDAT) ligands have been synthesized and studied. The structures of the new compounds are discussed on the basis of their spectroscopic and thermal data. Thermoanalytical studies of these compounds have shown a dependence of the thermal stability on the size of the metal cation; the PAT complexes have greater thermal stability than the others.

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Zusammenfassung Komplexe von Zn(II), Cd(II) und Hg(II) mit Phosphoramidothioat (PAT), Phosphorodiamidothioat (PDAT) und N,N-Diphenylphosphorodiamidothioat (N,N-DPDAT) als Liganden wurden synthetisiert und untersucht. Die Strukturen der neuen Verbindungen werden basierend auf deren spektroskopischen und thermischen Daten diskutiert. Die thermoanalytische Untersuchung dieser Verbindungen hat eine Abhängigkeit der thermischen Stabilität von der Größe der Metallkationen ergeben, und zwar sind die PAT-Komplexe thermisch stabiler als die anderen.

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, , N,N . N,N . . . .

     

Independence of chemical reactions

Up to this time the existence of physically true dependences between elementary reactions has been a returning question. The goal of this paper is to show that the real elementary reactions of a mechanism are practically independent. Introducing the concept of the space-time volume of a reaction (the reciprocal of the reaction rate) it is shown that, except for extremely fast processes (explosions), the reactions form very dilute systems. This systems must be ideal in the sense that interactions between elementary processes are very rare. The system exhibits some analogies with a dilute gas or solution. The extents of interactions can be calculated and the limits of independence estimated in this way.

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Simple catalytic mechanism permitting a multiplicity of catalyst steady states

The conditions of the existence of several steady states for a three-step mechanism, viz. a catalytic trigger (consecutive), are discussed.

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Catalytic and acidic properties of different metal-zeolite catalysts

Catalytic and acidic properties of bifunctional catalysts containing faujasite, superhigh-silica zeolite and mordenite have been studied in isomerization of C₈-alkylaromatic hydrocarbons.

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Selective synthesis of amylenes: Effect of catalyst alkali exchange and activation temperature on products distribution

The effect of Na-exchange and catalyst activaton temperature for selective synthesis of amylenes has been studied using a pretreated bentonite as catalyst. The selectivity to 3-methyl-1-butene rose with the catalyst activation temperatures. The alkali-exchange had a similar influence. The Na-catalyst was more selective to less substituted products, but their activity was lower than that of acidic catalysts.

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Na . 3--1 . . , , , .

     

Choice of conditions for activity measurements of commercial methanation catalysts

A method to choose the conditions of activity measurements for commercial methanation catalysts is suggested.

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Thermochemical studies on organic eutectics and molecular complexes

The phase diagrams of the binary systems of picric acid with naphthalene, anthracene and phenanthrene, and of -naphthol withp-toluidine, determined by the thaw-melt method, show the formation of a molecular complex and two eutectics in each system. The heats of the pure components, eutectics and molecular complexes were determined by differential scanning calorimetry. Comparison of the experimental heats of fusion with the theoretical values calculated via the mixture law suggests cluster formation in the melts. The entropy of fusion, enthalpy of mixing and excess thermodynamic functions were also calculated from the heat of fusion data.

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Zusammenfassung Die Phasendiagramme der binären Systeme von Pikrinsäure mit Naphthalin, Anthrazen und Phenanthren sowie von -Naphthol mit p-Aminotoluol wurden bestimmt. In jedem System zeigt sich die Bildung eines Molekülkomplexes sowie je zwei Eutektika. Mittels DSC wurden die Schmelzwärmen der reinen Komponenten, der eutektischen Mischungen und der Molekülkomplexe ermitteis. Der Vergleich der experimentell ermittelten Schmelzwärmen mit den mittels der Mischungsregel errechneten Werten läßt auf eine Clusterbildung in der Schmelze schließen. Weiterhin wurden aus den Schmelzwärmen auch Werte für Schmelzentropie und Mischungsenthalpie errechnet.

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Thanks are due to Prof. I. S. Ahuja, Head, Chemistry Department, Banaras Hindu University, for providing research facilities. Thanks are also due to CSIR, New Delhi, for financial assistance.     

Time dependence of the rate constant in the free radical oxidation in solid phase

ESR studies of oxidation kinetics of ethyl and dimethylpentyl radicals have been performed in glassy deuterium-containing alcohols, toluene-d₈ and in glassy 2,4-dimethylpentane-h₁₆, respectively. The kinetics is interpreted by assuming time-dependent reaction rate constant.

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, -d₈ 2,4--h₁₆. .

     

Etude des proprietes thermodynamiques et caracterisation des formes allotropiques du soufre condense dans un milieu poreux

Résumé L'analyse par diffractionX a montré que le soufre retenu dans une matrice mésoporeuse se trouve essentiellement sous la forme orthorhombique et conserve cette structure cristalline jusqu'à la fusion. L'analyse calorimétrique a confirmé pour ce métalloÏde les résultats théoriques régissant le changement d'état liquide solide et a permis d'en déterminer les paramètres: entropie de fusion et énergie interfaciale liquide-solide _ls. Cette étude thermodynamique a montré en outre qu'il était possible de prévoir dans le cas d'un soufre divisé par condensation dans un milieu poreux, une modification du domaine de stabilité des formes allotropiques.

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The X-ray analysis of sulphur held in a mesoporous material reveals essentially an orthorhombic crystalline structure. This form does not undergo phase transition before melting.The calorimetric analysis of such a divided sulphur corroborates the theoretical results which were established for liquid solid transformation inside a porous material in a previous paper. Moreover, this analysis helps determine its melting entropy and the solid-liquid surface tension _ls of sulphur.A thermodynamic study also permits a predetermination of the stability range of and allotropic forms in the case of divided sulphur.

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Zusammenfassung Die Röntgenanalyse von in halbdurchlÄssigem Material gehaltenem Schwefel zeigt im Wesentlichen eine orthorhombische Kristallstruktur. Diese Form erfÄhrt keinen Phasenübergang vor dem Schmelzen. Die kalorimetrische Analyse eines so verteilten Schwefels erhÄrtete die theoretischen Ergebnisse, welche in einem vorangegangenen Artikel für Flüssigfest-Umwandlungen im Inneren eines porösen Materials dargelegt worden sind. Ausserdem ermöglicht diese Analyse die Schmelz-Entropie und die Festflüssig-OberflÄchenspannung _ls des Schwefels zu bestimmen. Eine thermodynamische Studie gestattet auch die Voraussage zum StabilitÄtsbereich der und allotropischen Formen von verteiltem Schwefel.

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Interaction between particles in solution and the mechanism of dihydrogen activation in base catalyzed isotope exchange reactions

A previously suggested mechanism for the H-D isotope exchange of dihydrogen with aqueous alkaline and amide-ammonia solutions is discussed to be generalized and extended to hydrogen isotope exhange with other protolytic solvents.

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Conversion of dehydrolinalyl acetate in catalytic hydrogenation on metals

Low selectivity of dehydrolinalyl acetate (DeHLA) hydrogenation into linalyl acetate and ester group detachment are predicted in accordance with quantum-chemical data obtained for its homologue dimethyl ethynyl carbinol acetate. Experimental data are confirmed by theoretical calculations. DeHLA hydrogenation produces a variety of products.

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On the structure and activity of a Pt/C catalyst subjected to repeated deactivation and regeneration cycles

Electron microscopic studies reveal that repeated air/hydrogen regeneration cycles cause irreversible structural changes of a Pt/C catalyst involving sintering and migration of the platinum over the support. This is reflected by a serious decrease of the catalytic activity. With hydrogen treatment only, these effects are less significant.

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, / Pt/C, . . .

     

Kinetics of dehydrogenation of low aliphatic alcohols on copper catalysts containing small amounts of Cr, Mn, Fe and Ni

The apparent activation energy of dehydrogenation of ethyl, n-propyl, i-propyl, n-butyl and 2-butyl alcohols on Cr, Mn, Fe and Ni catalysts was correlated with the connectivity index of reactant molecule and the magnetic susceptibility of the catalyst. The dehydrogenation reaction seems to be favored by increasing catalyst paramagnetism.

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Effect of support on the stabilization energy of Pt, Pd and Ru

Stabilization energies of Pt, Pd and Ru on oxide supports have been determined by the interacting bond method. Supports to ensure better dispersity of metals are suggested.

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Characterization of MoS2/SiO2 by ESR and NO adsorption

Six MoS₂/SiO₂ samples were characterized by XRD, BET surface area, ESR and NO adsorption measurements. Correlation was found between the amount of Mo⁵⁺, sulfur radicals and adsorption capacity for oxygen and NO.

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MoS₂/SiO₂ , , , NO. Mo⁵⁺, NO.

     

Photocatalytic effects of trace metals evidence against a free radical chain mechanism in sulfite autoxidation

Autoxidation of sulfite is not a free radical chain reaction as generally assumed. High quantum yields found in the photoinitiated reaction are due to catalysis by unstable Fe(II) produced photochemically from Fe(III). Iron (III) is always present as trace impurity in the background of the reaction system.

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Calorimetric study of the interaction of oxygen with Pd-black and Pd/Al2O3

The kinetics of molecular hydrogen oxidation by palladium(II) has been studied under homogeneous conditions, excluding Pd-black formation. The rate constants for PdCl_i(H₂O)_4–i complexes for i=0, 1, 2, 3 and 4 are 0.12±0.003; 3.4±0.4; 5.2±0.3; 2.34±0.07 and 0 M^–1s^–1, respectively.

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, Pd-, H₂ (II). PdCl_i(H₂O)_4–i 0,12±0,003; 3,4±0,4; 5,2±0,3; 2,34±0,07 0 ^{–1 –1}, .

     

Low temperature oxidation of isobutene on heterogeneous photoimmobilized copper-containing catalysts

A new photoimmobilization method to synthesize heterogeneous metal complex catalysts for low temperature oxidation of isobutene to methacrolein is suggested. The process selectivity is 100%.

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Relation between the catalytic and acidic properties of zeolite catalysts

Influence of the strength and concentration of non protic centers on the catalytic activity of metal-zeolite catalysts in isomerization of n-butane has been studied. A relationship between the specific activity and the center strength is suggested.

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