General equation for dissociative heterolytic reaction rates and corrections to the Br?nsted relationship

A general equation is proposed for the rates of halide and H⁺ ion transfer. A relay-type participation of H₂O in the transfer of H⁺ in aqueous solutions is substantiated.

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: - H⁺. H₂O H⁺ .

     

Synthesis and Dehydrohalogenation of 3 β-Chloro-5 α,7 α-dibromo-6-ketosteroids of the Stigmastane and Cholestane Series

3-Chloro-5,7-dibromo-6-ketosteroids 5a and 5b are synthesized from -sitosterol (1a) and cholesterol (1b). Dehydrohalogenation of these forms 7-bromo-2,4-dien-6-ones (6a-b), 2,4-dien-6-ones (7a-b), and 14-hydroperoxy-2,4,7-trien-6-ones (8a-b). Woodward hydroxylation of dienone 6a produces 2-iodo-7-bromo-3-acetoxy-⁴-6-ketone 9 and 7-bromo-2,3-diacetoxy-⁴-6-ketone 10. 2-Iodo-3-acetoxy-^4,7,14-trien-6-one 11 is prepared analogously from trienone 8a.     

Investigation of proton-acceptor properties of oxide surfaces by IR spectroscopy of hydrogen-bonded complexes

Strength of the basic centers on catalyst surfaces is suggested to be characterized by the IR spectra of adsorbed chloroform. The existence of centers with different proton-acceptor properties on several oxides is shown experimentally.

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- . , .

     

Kinetics of the catalytic transformation of isobutene into methacrylonitrile with NO on supported nickel oxide aerogel

Kinetic studies of the nitroxidation of isobutene by NO show that the reaction follows a redox mechanism in the temperature range of 300–400°C. This mechanism implies an interaction between dehydrogenated isobutene -allyl radical and atomic nitrogen due to the decomposition of NO by the reduced catalyst, which is then reoxidized.

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NO , 300–400°C. - , NO , .

     

Catalytic oxidation of cycloalkane heteroanalogs as a way to polyfunctional compounds

Liquid phase oxidation of cycloalkane diheteroanalogs catalyzed by compounds of Cu²⁺, Ni²⁺, Co²⁺, Cr³⁺, Fe³⁺ has been studied. It has been established that these catalysts can be applied to intensify, oxidize and increase the selectivity of this process.

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: Cu², Ni²⁺, Co²⁺, Cr³⁺, Fe³⁺. .

     

State of copper in massive Cu?V?Mo oxide systems

ESR data for X(CuO) V₂O₅·8.3 MoO₃ system heated at 400–550 °C indicate the occurrence of a copper state with d_Z ²-ground state. Copper ions are orbitally ordered apparently in –Cu²⁺–O–Cu¹⁺–O–Cu²⁺-chains.

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B X(CuO) V₂O₅·8,3 MoO₃ , 400–550°C d_Z ²- . , , –Cu²⁺–O–Cu¹⁺–O–Cu²⁺-.

     

Monohalogenobenzoylhydrazones VI. New antimony(III) complexes with monochlorobenzoylhydrazones of 2-furaldehyde, 2-pyrrolaldehyde and 2-thiophenaldehyde as ligands

The antimony(III) trihalides, SbX₃ (X=Cl, Br and I), react with the title ligands to give the compounds SbX₃L, where L=benzoyl- and monochlorobenzoylhydrazones of 2-furaldehyde (FBHH and FClBHH), 2-pyrrolaldehyde (PBHH and PClBHH) and 2-thiophenaldehyde (TBHH and TClBHH). The characterization of the new species was based on their elemental analyses, spectral data (IR and UV-Vis) and thermal studies. The ligands appear to offer two coordination sites (the carbonyl and azomethine groups) and perhaps a third one (the heteroatom of the heterocyclic ring). The thermal decompositions of the studied complexes proceed via one or three stages, the number of stages depending on the nature of both the hydrazones and the halogens. The structures proposed for the investigated complexes are either pseudo- or distorted octahedral.

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Zusammenfassung Antimon(III)-trihalogenide, SbX₃ (X=Cl, Br und I) reagieren mit den Titelliganden und liefern Verbindungen der allgemeinen Formel SbX₃L (L=Benzoylbzw. Monochlorobenzoylhydrazon von 2-Furfuraldehyd (FBHH und FClBHH), von 2-Pyrrolaldehyd (PBHH und PClBHH) und von 2-Thiophenaldehyd (TBHH und TClBHH). Die neuen Verbindungen wurden mittels Elementaranalyse, Spektraldaten (IR und UV) sowie thermischen Untersuchungen beschrieben. Zwei Koordinationsstellen scheinen von den Liganden bevorzugt zu sein: die Carbonylund die Azomethingruppe. Eine dritte könnte das Heteroatom des heterocyclischen Ringes sein. Die thermische Zersetzung der untersuchten Komplexe vollzieht sich in Abhängigkeit von der Natur der Hydrazone und der Halogene in einem oder in drei Schritten. Als Struktur für die untersuchten Komplexe wird eine pseudo-oder verzerrte oktaedrische Struktur vorgeschlagen.

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SbX ₃ (X=Cl, Br, I) - , 2- 2- , SbX ₃ L. , ( ), . , , . . .

     

Temperature programmed desorption of NH3 and H2O from NH4NaX and CoNH4NaX zeolites

A study has been made of temperature programmed desorption (TPD) of NH₃ and H₂O from samples of NH₄X and CoNH₄X zeolites of various degree of exchange. NH₃ TPD peaks could be explained by interaction of NH₃ with different Brönsted and Lewis acidic centers. Moreover a water peak at high temperatures allowed interpretations of the dehydroxylation, and by reason of the characteristic desorption temperatures a particular state of the Co²⁺ ions in the CoNH₄X zeolites is postulated.

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- () NH₃ H₂O NH₄X CoNH₄X . NH₃ NH₃ =qs . . Co²⁺ CoNH₄X.

     

Unimolecular decomposition of CF3OF-calculation by reduced Kassel integral in factorized form

The fall-off curves were calculated for the unimolecular decomposition of the trifluoromethyl hypofluorite at 475.8, 496.9 and 507.3 K by means of the Reduced Kassel Integral in Factorized Form.

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475,8,496,9 507,3 .

     

ESR studies on stabilized cool flame of propylene

In the oxidation of propylene a sharp change in the concentration of radicals, observed when passing from the slow reaction region to cool flames, indicates the chain character of the cool flame. Unlike propane and butane, the temperature dependence of the radical concentration and the maximum self-heating are practically unchanged within 603–663 K.

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. , . , 603–663 , .

     

Investigation of isomerization of n-pentane over supported Pt catalyst modified by adsorbed Bi and Pd

-Al₂O₃-supported Bi–Pt and Pd–Pt bimetallic catalysts were prepared by electrochemical metal adsorption. Isomerization of n-pentane was studied over these catalysts in a pulse reactor. It can be concluded from the results that the properties of these catalysts differ substantially from the base Pt/-Al₂O₃ catalyst. On the modified catalysts conversion and the yield of i-pentane was found to be lower although selectivity was better. The ratio of cracking reactions was also lower than over the base catalyst.It is very probable that the adsorbed bismuth was slowly desorbing from the catalyst surface during the experiments.

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Bi–Pt Pd–Pt -Al₂O₃. -, . , Pt/Al₂O₃. , - , . , . , .

     

Effect of free phosphine on the reactivity of phosphine-containing rhodium(I) complexes

The photolysis products of SO₂-pentane-NO mixtures are N₂O, H₂O and a compound designated as RNO. Kinetic data obtained by OC method confirm the previously proposed scheme of photolysis. Also studied was the photolysis of SO₂, NO and cyclohexane mixtures. From comparison of spectral characteristics of RNO and its analog 2-methyl-2-nitrosopropane, the probable structure of RNO is suggested.

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SO₂--NO N₂O, H₂O , RNO. , , . SO₂ NO . RNO 2--2- RNO.

     

Kinetics and mechanism of the permanganate oxidation of trans-crotonic acid

The kinetics and intermediates of the permanganate oxidation of trans-crotonic acid have been investigated in the pH range of 0.5–5.0 using the stoppedflow technique. The formation of manganese(III) as a short-lived intermediate has been established. The reaction is first order with respect to both MnO ₄ ^– and crotonic acid (crotonate). The resolved rate constants at 25°C are 730 and 410 M^–1 sec^–1 for the acid and the anion, respectively. The reaction mechanism is discussed.

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pH=0,5–5,0, . (III) . MnO ₄ ^– , (). 25°C 730 410 M^{–1 –1} , . .

     

Studies of coke distribution in high-silica ZSM zeolites

A method for studying coke distribution in zeolites is suggested. It has been established that two forms of coke can form: one is intracrystalline and the other is located on the outer surface of ZSM zeolites.

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. : ZSM.

     

Investigations on the compatibility of milk fat fractions and lauric fats

The compatibility of a lauric fat with several milk fat fractions (MF) was investigated. The enthalpy of crystallization was measured by differential scanning calorimetry (DSC). These values were related to the corresponding values calculated for an Ideal Blend. The different compatibility of the milk fat fractions with the lauric fat could be shown by this method very clearly.

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Untersuchungen zur Mischbarkeit/Verträglichkeit von Milchfettfraktionen mit laurischen Fetten

Zusammenfassung Die Mischbarkeit/Verträglichkeit von Milchfettfraktionen mit einem laurischen Fett wurde differenzkalorimetrisch untersucht. Die Auswertung der Befunde bezieht sich auf die entsprechenden Rechnungswerte einer Idealen Mischung. Es wurde nachgewiesen, da sich diese Milchfette deutlich in ihrer Mischbarkeit unterscheiden.

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. $ . , $ - . $ .

     

On the thermal analysis of aliphatic carboxylic acids and their salts

The thermal behaviour of oxalic, malonic, succinic, glutaric, adipic, pimelic, suberic, azelaic and sebacic acid, and of their mono- and disodium salts and calcium salts has been studied by derivatography. Some of the acids were distilled off without decomposition, while the others were decomposed in accordance with the rule of Blanc.Up to 600°, the decomposition of the monosodium salts consists of two principal steps. The first process is the liberation or the decomposition of the acid formed from the salt, the second step the decomposition of the normal salt into sodium carbonate and organic molecules. This decomposition mechanism was verified also by tracer technique on compounds labelled with the¹⁴C isotope. With most of the compounds unable to form ketones, the decomposition of the normal salt yields a great variety of organic compounds. In the case of adipates and pimelates the formation of cyclanones predominates.

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Zusammenfassung Es wurde das thermische Verhalten von Oxalsäure, Malonsäure, Bernsteinsäure, Glutarsäure, Adipinsäure, Suberinsäure, Azelainsäure und Sebacinsäure, sowie ihrer Mono- und Dinatrium- und Calciumsalze derivatographisch untersucht. Einige dieser Säuren destillierten ohne Zersetzung, die übrigen zerlegten sich entsprechend dem Blancs'schen Gesetz.Die Zersetzung der Mononatriumsalze verlief bis 600° in zwei Stufen. In der ersten wurde die salzbildende Säure freigesetzt oder zersetzt, in der zweiten zersetzte sich das normale Salz in Natriumkarbonat und in organische Moleküle. Der Zersetzungsmechanismus wurde mit durch¹⁴C markierten Verbindungen kontrolliert. Bei der Zersetzung der normalen Salze und der Verbindungen, die unfähig sind Ketone zu bilden, entstehen mannigfaltige organische Verbindungen. Im Falle von Adipaten und Pimelinaten überwiegen Cyclanone.

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Résumé On a étudié par dérivatographie le comportement thermique des acides oxalique, malonique, succinique, glutarique, adipique, pimélique, subérique, azélaique et sébacique, et de leurs sels mono et disodiques et de calcium. Certains de ces acides distillent sans décomposition, alors que d'autres se décomposent suivant la loi de Blanc.La décomposition du sel monosodique se déroule en deux étapes jusqu'à 600°. Dans la première, l'acide formant le sel se dégage ou se désompose; dans la deuxième, le sel normal de sodium se décompose en donnant du carbonate de sodium et des molécules organiques. Le mécanisme de la décomposition a été vérifié à l'aide de combinaisons marquées par le¹⁴C.La décomposition des sels normaux et des combinaisons impropres à donner des cétones fournit une grand variété de composés organiques. Dans le cas des adipates et des pimélates, la formation de cyclanones prédomine.

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, , , , , - . , . 600° . , , — « » . , C¹⁴ . . .

     

Precipitation of iron catalysts for the Fischer-Tropsch synthesis

The batch Fischer-Tropsch wise precipitation of iron catalysts for the synthesis in the pH range of 4.60 to 7.91 is described in detail. Each step of the precipitation has been controlled by measurements of the relevant parameters to produce definite catalysts. Factors influencing the reproducibility are shortly discussed.

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- pH=4,60–7,91. . , .

     

Effects of admixtures of potassium bromide on the thermal decomposition of potassium bromate

The effects of admixtures of potassium bromide (2.5% and 5%) on the thermal decomposition of potassium bromate were studied within the temperature range 653–683 K. The fraction decomposed() vs. time (t) relations revealed (i) initial gas evolution, (ii) acceleratory and (iii) decay steps. The data were analysed on the basis of the first-order law with two rate constantsk ₁ andk ₂,k ₁ being the rate constant for the initial, slow first-order process (0.02, 0.26), andk ₂ being the rate constant for the subsequent faster process, holding within the range 0.21 to 0.98. Upon increase of the concentration of added potassium bromide to 5%, the range for the slow and faster processes became 0.01 to 0.16 and 0.1 to 0.98, respectively. At a given temperature,k ₁ increased with increasing bromide concentration, whereask ₂ almost identical for pure potassium bromate and its mixtures (2.5% and 5% bromide).

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Zusammenfassung Im Temperaturbereich von 653–683 K wurde der Einfluß von Beimengen von Kaliumbromid (2,5% und 5%) auf die thermische Zersetzung von Kaliumbromat untersucht. Die Funktion der zersetzten Menge () in Abhängigkeit von der Zeit (t) weist eine anfängliche Gasentwicklung(i), eine beschleunigte(ii) und eine abklingende Stufe(iii) auf. Die Daten wurden auf der Grundlage einer Kinetik erster Ordnung mit den zwei Geschwindigkeitskonstantenk ₁ undk ₂ durchgeführt, wobeik ₁ die Geschwindigkeitskonstante für den einleitenden, langsameren Schritt erster Ordnung ist (0,02, 0,26) undk ₂ die Geschwindigkeitskonstante für den darauffolgenden schnelleren Vorgang mit Werten zwischen 0,21 und 0,98. Bei Erhöhung der Konzentration von Kaliumbromid auf 5% betrug der Bereich für den langsameren und den schnelleren Vorgang 0,01 bis 0,16 bzw. 0,10 bis 0,98. Bei gegebener Temperatur steigtk ₁ mit zunehmender Kaliumbromidkonzentration an, währendk ₂ für reines Kaliumbromat und seine Mischungen mit 2,5% und 5% Kaliumbromid fast identisch bleibt.

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653–683 (2,5 5%) . , . k ₁ k ₂, ( 0,02 0,26), - 0,21–0,98. 5% k ₁ k ₂ , , 0,01–0,16 0,1–0,98. k ₁, , k ₂ , (2,5 5%) .

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The work is dedicated to the memory of the late Prof. S. R. Mohanty.     

Catalytic properties of cobalt and manganese complexes with macromolecular ligands in the liquid-phase oxidation of ethylbenzene

The selective catalytic effect of transition metal complexes (in particular cobalt and manganese) with polymeric ligands is shown on the example of the liquid-phase oxidation of ethylbenzene. The catalytic activity depends on both the structure of the polymeric matrix and the nature of metal.

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( ) . , , .

     

Effect of explosion on the catalytic activity and selectivity of natural fluorite

The effect of various types of shock waves on the catalytic activity of natural fluorite in isopropanol dehydrogenation and dehydration reactions has been studied. Shock treatment is shown to decrease the catalytic reaction temperature and to increase the selective

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. , .