Allowance for polarization of atomic electron shells in MO LCAO calculations

The application of MO LCAO methods to molecules containing elements in the higher periods is discussed, especially compounds containing two phenyl rings linked via an oxygen atom. The calculated -electron density is found to agree with the observed electronic absorption spectra, dipole moment, effects of polarity on reactivity, and so on, provided that the wave function used for the heteroatom with n>2 is =c₁ npz+ +c_{2 nd}+...; the terms c_{2 nd}... provide correction for the change in the atomic function _npz produced by the surrounding atoms. This effect is not important for O, N, and C (first period). The effects of surrounding atoms on _npz for the halogen atom have evidently to be considered in computations on the -electron density for any molecule containing such an atom.     

Thermal analysis of poly(methyl methacrylate)-copper composite

Thermal characteristics of the composites of poly(methyl methacrylate) and copper are reported, including the order of reaction and activation energy of the major second stage of pyrolysis. The randomly-distributed metal particles in the polymer matrix can form paths for heat transfer which determine the mechanism of thermal degradation.

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Zusammenfassung Die thermischen Charakteristika der Verbindungen von Polymethylmethacrylat mit Kupfer werden zusammen mit der Reaktionsordnung und der Aktivierungsenergie der grösseren zweiten Stufe der Pyrolyse beschrieben. Die zufallsbestimmt verteilten Metallpartikel in der Polymermatrix können Wege des Wärmetransfers formen, welche den Mechanismus der thermischen Zersetzung bestimmen.

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Résumé On décrit les caractéristiques thermiques de composites du polyméthylméthacrylate avec le cuivre, parmi lesquelles l'ordre de réaction et l'énergie d'activation de la seconde étape de la pyrolyse qui est la principale. Les particules du métal distribuées au hasard dans la matrice du polymère peuvent constituer des voies pour le transfert de chaleur qui déterminent le mécanisme de la dégradation thermique.

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, . , .

     

ESR spin-trapping study of the radicals produced in the photochemical reaction of Cr, Mo, W hexacarbonyls with carbon tetrachloride

The effect of UV and visible light on the catalytic reaction has been investigated in the systems containing Cr, Mo and W hexacarbonyls, nitrone and nitroso type of spin-traps in carbon tetrachloride. Under these reaction conditions not only radical CCl ₃ ^. but also dialkyl-, diphenyl- and acyl-phenylnitroxides have been trapped.

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, Cr, Mo W, . CCl ₃ ^. , , .

     

Role of rhenium in bimetallic reforming catalysts

The influence of rhenium on the behavior of a Pt/Al₂O₃ catalyst was studied in n-hexane reaction by means of dilution of the catalyst bed with Re/Al₂O₃. Parallel to activity, selectivity and ageing data obtained in slug pulse and continuous flow reactors, the amount of the surface carbon formed during the reaction was determined and its reactivity in hydrogen atmosphere was also studied. It is suggested that in the presence of rhenium due to the increase in the amount of hydrogen available for hydrogen consuming reactions including hydrodepolymerization of the carbonaceous surface overlayer, the routes of ageing processes are changed, resulting in lower carbon content on the catalyst and less pronounced catalyst deactivation.

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Pt/Al₂O₃ -, Re/Al₂O₃. , , , , . , , , , , , , .

     

Kinetics and mechanism of hydrazine oxidation by oxygenated Co2(L-his)4O2 complex

The kinetics of Co₂ (L-his)₄O₂ reduction by hydrazine in aqueous solution has been studied and the rate constants, the energy and entropy of activation have been determined.

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, , Co₂ (L-)₄O₂ .

     

Esterification in solution. The reaction of methacrylic acid with glycols

Azeotropic methacrylation of ethylene glycols in solution in the presence of p-toluenesulfonic acid can be described by two irreversible consecutive-competitive second order reactions with a rate constant ratio of to 2. The main reaction may be complicated by esterification of p-toluenesulfonic acid. Under certain conditions this side reaction may become predominant. A possible reason of this phenomenon is suggested.

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- - 2. -. . .

     

Dehydrogenation of tetralin on cobalt and nickel modified type X zeolites

The dehydrogenation of tetralin on cobalt and nickel modified NaX zeolites has been studied in a flow system at atmospheric pressure and 390–430 °C. A method for comparing the activity of the zeolite catalysts is proposed.

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NaX , 390–430 °C. .

     

Comparison of thermal characteristics of materials examined by thermogravimetry and flammability tests

This paper deals with the examination of various types of flame resistant fabric in fire conditions, standard flammability tests and thermogravimetry. It shows how it may be possible to determine the protection afforded by a garment using very small samples and instrumental laboratory techniques. This could be important in the development of new materials where a quick assessment could be made of the protective qualities of the material.

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Zusammenfassung Es wird die Prüfung verschiedener feuerfester Gewebe unter Feuerbedingungen bei standardisierten Entzündbarkeitsprüfungen und durch Thermogravimetrie beschrieben. Es wird gezeigt, wie der durch ein Kleidungsstück gewährleistete Schutz mit sehr kleinen Proben und durch Laboratoriumstechnik bestimmt werden kann. Dies könnte bei der Entwicklung neuer Materialien von Wichtigkeit sein, wo eine Schnellbestimmung der Schutzeigenschaften des Materials durchgeführt werden muß.

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Résumé On examine différents types d'étoffes ignifuges du point de vue de l'inflammabilité et par thermogravimétrie. On montre la possibilité de déterminer à l'aide des techniques instrumentales de laboratoire, l'action protectrice d'un vêtement en utilisant de très petits échantillons. Cela pourrait être important lors du développement de matériaux nouveaux oú l'on pourrait soumettre à analyse rapide les qualités protectrices des étoffes.

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, . , , . , .

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We wish to express our thanks to the Air Force Materials Laboratory, Air Force Systems Command, U.S. Air Force for the sample of PBI and to the Council and Director of LIRA for their permission to publish this paper.     

Partial kinetic models in the H2?O2 system

Using the concepts of maximum mechanism and non-equilibrium free energy, some partial kinetic models of hydrogen oxidation have been found by means of solving a direct kinetic problem. It is shown that the basic difference in the kinetic models of ignition is the initial period of the process (induction period) while the mechanism of the well-developed process slightly depends on the initial conditions and remains mainly the same for the parameters under study.

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H₂–O₂ ( ) . , ( ), , .

     

2-Amino-4-[2-(5-nitro-furyl)vinyl]thiazole and its derivatives

The reactions of 4-bromo-1-(5-nitro-2-furyl)but-1-en-3-one and its 2-methyl and 2-chloro derivatives with thiourea and its N-allyl and N-phenyl derivatives have yielded 2-amino-4-[-5-nitro-2-furyl)-vinyl]thiazole and its - and N-substituted derivatives. 2-Amino-4-[-(5-nitro-2-furyl)vinyl]thiazole and its -methyl derivative have also been prepared by the direct reaction of the corresponding , -unsaturated ketones with bromine and an excess of thiourea in chloroform, as was shown by a comparison of UV spectra. A series of N-acyl derivatives of the aminothiazoles has been obtained. UV and IR spectra are given.     

Quinindines

The Mannich reaction and hydroxymethylation of -quinindane at the 3 position were studied. The dialkylaminomethyl derivatives readily split out dialkylamine to form 3-methylene--quinindane, the structure of which was proved by the IR, UV, and PMR spectra. The dipole moments and pK values of the compounds were measured. No tetracyclic compounds are formed; the reaction ceases at the step involving formation of N-phenacylido--quinindane.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1530–1534, November, 1970.     

AM1 study of photoelectron spectra

A correlation was found between the group dipole moments of substituents determined from the dipole moments of ethylene derivatives and the second ionization potentials of allene derivatives corresponding to the -MO of the C()-C() bond. It was shown that the concept of the effect of the substituent field cannot completely explain the observed phenomena, and the energies of the second ionic states of bromoallene and alkoxyallenes are lowered because of the interaction between nonbonded fragments through the systems of the compounds. It has been found that, in terms of orbital approximation, this interaction causes electronic destabilization of theanti-planar (trans) conformers of methoxyallene and methyl vinyl ether compared to theirsin-planar (cis) forms.For Part 5, see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 48–54, January, 1995.     

Intramolecular cyclization of N-phthalyl-β-aryl-β-alanine phenylhydrazide

The reaction of N-phthalyl--aryl--alanine N-methyl-N-phenylhydrazides with phosphorus oxychloride (at80 °C) is accompanied by further transformations of the initially formed 2-aminoindole derivatives and leads to isoindolo[1,22,3]-pyrimido[5,6-b]indole derivatives. Intermediate 2-aminoindoles were isolated at lower reaction temperatures. The hydrolysis of the isoindolo[1,22,3]pyrimido [5, 6-b]indole derivatives was studied. The structures of the compounds obtained were established on the basis of the PMR, IR, and UV spectra and the results of elementary analysis.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 926–929, July, 1982.     

Preparation and properties of cyclodextrin inclusion compounds of organometallic complexes. Ferrocene inclusion compounds

Inclusion compounds of ferrocene(FcH) and its derivatives with cyclodextrins(CDs; -CD, -CD, and -CD) were prepared. CD-ferrocene inclusion compounds were obtained in a crystalline state in high yield. -CD and -CD formed 11 stoichiometric inclusion compounds with ferrocene and its derivatives. -CD formed 21 (CD:guest) complexes with ferrocene and the monosubstituted derivatives, but did not form complexes with 1,1-disubstituted derivatives, -CD-FcH and -CD-FcH complexes are thermally stable and do not liberate ferrocene on heating at 100°C in vacuo. The cyclodextrin inclusion compounds were characterized by¹H-NMR, IR, UV, and CD spectra. A large positive induced Cotton effect was observed in the case of -CD-FcH complex, while the -CD-FcH complex showed a negative spectrum. The binding mode is discussed. -Cyclodextrin was found to form inclusion complexes in ethylene glycol, diethylene glycol, triethylene glycol, methyl cellosolve, ethyl cellosolve, methyl alcohol, and glycerine solutions. -CD also formed complexes in ethylene glycol solution. The binding of ferrocene by -CD is stronger in ethylene glycol than in dimethyl sulfoxide and dimethyl formamide.     

Prediction of Stability Constants for Cr(III) and Cr(II) Complexes

Regression analysis was used to derive equations for estimaing thermodynamic stability constants for complexes of Cr²⁺ (log^° ₁[Cr²⁺L] = 0.53log^° _n [H _n L]) and Cr³⁺ (log^° ₁[Cr³⁺L] = 0.88log^° _n [H _n L]) from the known protonation constants of H _n L ligands and for determining stability constants of Cr²⁺ and Cr³⁺ complexes from the available stability constants of Cu²⁺ complexes (log^° ₁[Cr²⁺L] = 0.76log^° ₁[Cu²⁺L] and log^° ₁[Cr²⁺L] = 0.60log^° ₁[Cr³⁺L], respectively). Parameters of the Panteleon–Ecka equation for calculating stability constants of Cr²⁺ complexes ( = 0.57) and Cr³⁺ complexes ( = 0.69) with two and three bidentate ligands were also determined. The ratio of logarithmic stability constants for complexes with the same metals but with different metal ionic charges was found to be approximately equal to the ratio of charges on the central ions. The stability constant of Cr(II) sulfate complex was calculated.     

Spectroscopic study of organosilicon derivatives of thiophene

The IR spectra of organosilicon derivatives of thiophene were investigated. A comparison of the results with the literature data made it possible to isolate the characteristic absorption bands of the substituted thiophene ring and to reveal some regularities in the IR spectra of thienylsilanes. The inductive constants of substituted thienyl groups were calculated from the experimental(Si-Cl) values. An analysis of the values shows that electron-donor substituents X lower the acceptor capacity of the thienyl substituent as a whole, while electron-acceptor substituents increase it.See [1] for communication IV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 477–481, April, 1974.     

Hydrazones

Conclusions Study of the IR spectra, and theoretical and experimental values of the dipole moment, has shown that the nicotinoyl- and isonicotinoylhydrazones exist as mixtures of the EE'E and EE'Z rotational forms of the syn isomer in solution; the salicylide derivatives as mixtures of the EE'Z and EZ'Z forms. The EEE form is sterically hindered by the intramolecular hydrogen bonding.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 335–339, February, 1977.     

Properties of a multiple bond conjugated with the pyridine ring

The products of the addition of diazomethane to the double bond of -, -, and -vinyl-pyridines, 2-propenyl-, 2-styryl-, and 2-(p-nitrostyryl)pyridines, and -(2-pyridyl)acrylic acid were obtained. When a hydrogen atom or alkyl or phenyl group is present in the -position of the vinyl group, 3-pyridyl-²-pyrazolines are formed (they are isolated as the acetyl derivatives). Electron-acceptor substituents (COOCH₃ and C₆H₄NO₂) in this position disrupt the polarization, and this leads to the formation of a mixture of two isomeric pyrazolines. The primary formation of ¹-pyrazolines was proved by means of IR and UV spectroscopy.See [1] for communication IX.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 64–69, January, 1973.