Adsorbed oxygen species formed by reaction with N2O on CaO

A considerable amount of adsorbed oxygen species is formed by the reaction of N₂O on CaO. It is suggested that these adsorbed species were practically held on 5-coordinated sites.

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- N₂O CaO. , 5-- .

     

Thermal decomposition of metal polyacrylates

Results of thermal and pyrolysis-GC/MS analyses of Na, Ca and Mg polyacrylates are presented. It was confirmed that the main decomposition reactions of the Na salt take place in the temperature range 420 – 470 and those of the other two polymers in the range 450–490. It was found that the solid residue after decomposition was the metal carbonate or oxide, while the volatile products consisted of H₂, CO, CO₂, saturated and unsaturated hydrocarbons (including cycloolefins and aromatic hydrocarbons) and aliphatic ketones. This suggests that the thermal decomposition of the metal polyacrylates proceeds via side-chain splitting and breaking of the main chain of the polymer, without retropolymerization.

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Zusammenfassung Die Ergebnisse der Thermo- und Pyrolyse-GC/MS-analysen von Na-, Ca- und Mg-Polyacrylaten werden beschrieben. Es wurde bestÄtigt, dass die Hauptzersetzungsreaktionen des Natriumsalzes im Temperaturbereich von 420 bis 470, jene der anderen zwei Polymeren im Bereich von 450 bis 490 ablaufen. Es wurde nach der Zersetzung ein fester Rückstand von Metallkarbonat oder -oxid gefunden, wÄhrend die flüchtigen Produkte aus N₂, CO, CO₂, gesÄttigten und ungesÄttigten Kohlenwasserstoffen (darunter Zykloolefinen und aromatischen Kohlenwasserstoffen) und aliphatischen Ketonen bestanden. Dies lÄsst darauf schliessen, dass sich die thermische Zersetzung der Metallpolyacrylate über die Abspaltung der Seitenkette und der Spaltung der Hauptkette des Polymers ohne Retropolymerisation vollzieht.

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Résumé On présente les résultats des analyses thermiques et des produits de décomposition pyrolytique par chromatographie en phase gazeuse et spectrométrie de masse (GC/MS) des polyacrylates de Na, Ca et Mg. On confirme que la réaction de décomposition principale du sel de sodium a lieu entre 420 et 470 et celle des deux autres polymères entre 450 et 490. On trouve que le résidu solide après décomposition est le carbonate ou l'oxyde du métal, tandis que les produits volatils consistent en N₂, CO, CO₂, en hydrocarbures saturés et non-saturés (y compris les cyclooléfines et hydrocarbures aromatiques) et en cétones aliphatiques. Cela permet de supposer que la décomposition thermique des polyacrylates métalliques s'effectue par coupure de la chaÎne latérale et par rupture de la chaÎne principale du polymère, sans rétropolymérisation.

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-- -- Na, Ca Mg. , 420–470, — 450–490. , . H₂, CO, CO₂, , , . , .

     

Optical and electrical measurements on CO2 covered copper films

Thin polycrystalline copper films are deposited in a special UHV cell on glass substrates and are covered step by step with CO₂. The optical and electrical properties of the films are studied in-situ by means of ellipsometry and resistivity measurements. The properties of the clean films correspond to literature data. In the case of monolayer adsorption of CO₂, the changes in the ellipsometrical angles are +1° and +0.1°, similar to the Cu/O and Cu/CO systems. Three-dimensional island growth leads to a drastical increase of and by several orders of magnitude. The resistivity first quickly decreases and then slowly reapproaches the initial value. This marked kinetics is quantitatively interpreted on the basis of a diffusion model.     

A simplified View of δ → δ* Transition Energies in Compounds with multiple metal-metal bonds: The isolated δ — δ* manifold model

The energetics of the * transition in quadruply bonded complexes are investigated using a very simple valence-bond formalism, called the isolated * manifold (IDDM) model. In this model all electrons except for those that occupy the or * molecular orbitals are ignored, as are explicit metal-ligand interactions. The resulting equations allow the calculation of transition energies very inexpensively, albeit with poor quantitative agreement: the * transition in prototypical quadruple-bond systems is predicted to occur at energies greater than 70,000 cm¹. The model incorporates configuration interaction between the two¹ A _1g configurations (|| and |**|) to roughly the same extent as do correlated all-electron calculations. The application of the method to systems that involve relative changes in * transition energies, such as the torsional twisting of quadruple bonds, is more successful quantitatively.     

Rate constants for the interaction of trifluoromethyl radicals with oxygen and fluorine

The absolute rate constants for the reactions of trifluoromethyl radicals with fluorine (I) and oxygen (II), k₁=(3.1±2.1)×10^–11 exp [–(4600±300)/RT] (cm³/molec sec) and k₂=(2.5±1.7)×10^–11 exp [–(2100±300)/RT] (cm³/molec sec). have been determined from the relative rate constants for the reactions of trifluoromethyl radicals with oxygen and chlorine (IV):k₂/k₄=(3.6±1.6)exp [(1600±300)/RT] (T=269–356 K) obtained by the photolysis of a mixture of hexafluoroacetone (HFA) with O₂ and Cl₂.

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(I) (II) k₁=(3,1±2,1)·10^–11 exp[–(4600±300)/RT] (cm³/. ), k₂=(2,5±1,7)·10^–11 exp[–(2100±300)/RT] (cm³/. ) O₂ Cl₂ (І) k₂/k₄=(3,6±1,6)exp[(1600±300)/RT](T=296–356° K).

     

Untersuchung binärer metallischer Systeme mit Hilfe des Amalgamverfahrens. Das System Nickel-Zinn

Zusammenfassung Eine unter Anwendung des Amalgamverfahrens durchgeführte Untersuchung des Systems Nickel-Zinn ergab bis 50 At.-% Zinn sehr gute Übereinstimmung mit dem Schmelzdiagramm. In Legierungen mit höherem Zinngehalt wurden jedoch, abweichend von den Ergebnissen bisheriger Untersuchungen, zwei einander strukturell sehr ähnliche Phasen und ₁ mit schmalem Homogenbereich aufgefunden. Die -Phase ist identisch mit der bereits in Schmelzlegierungen festgestellten monoklinen Kristallart; ihre Zusammensetzung ist aber gegenüber dem Schmelzdiagramm gegen die Nickelseite hin verschoben.Die zinnreichere ₁-Phase ist von der -Phase durch einen heterogenen Bereich von nur 2,5% getrennt. Bei höheren Temperaturen tritt eine Aufweitung des - und eine Verengung des ₁-Gebietes ein, wobei der zwischen diesen Phasen liegende heterogene Bereich noch schmaler wird; er umfaßt bei 600° nur mehr 0,5%.Mit 3 Abbildungen.Herrn Prof. Dr.A. Klemenc zum 70. Geburtstag gewidmet.     

Temperature dependence of the volumetric properties of binary mixtures containing oxaalkane +n-heptane

Excess molar volumes of mixtures of n-heptane + 2,5-dioxahexane and n-heptane + 2,5,8-trioxanonane were determined from density measurentents at 5, 15, 25 and 35°C. These results allowed the following mixing quantities to be reported in all range of concentrations: , (v ^E /T) _P and (h ^E /P) _T , at 25°C. The obtained values were then compared with the calculated values by using the Flory theory and the Nitta-Chao theory of liquid mixtures. The results are discussed in terms of order or disorder creation.     

Role of three phonon normal processes in the analysis of the thermal conductivity of solid HD at low temperatures

The role of the three phonon normal processes in the analysis of the lattice thermal conductivity of the solid HD has been studied in the entire temperature range 0.2–4 K. The study is made by calculating the contribution of the correction term due to the three phonon normal processes towards the total lattice thermal conductivity of the pure sample of the solid HD in the temperature range stated above. The study is also made for the different values of the three phonon normal processes scattering relaxation rate. The considerable contribution due to the correction term is found compared to the total phonon conductivity above 1 K.

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Zusammenfassung Die Rolle der Drei-Phonon-Normalprozesse in der Analyse der Gitter-Wärmeleitung von festem HD wurde im Temperaturbereich von 0.2 bis 4 K untersucht. Die Untersuchung wurde durch Berechnung des Beitrages des den Drei-Phonon-Normalvorgängen zuzuschreibenden Korrekturterms an der totalen Gitter-Wärmeleitung der reinen Probe des festen HD im o.a. Temperaturbereich durchgeführt. Diese Betrachtung wurde auch für die verschiedenen Werte der Streuungsrelaxationsgeschwindigkeit der Drei-Phonon-Normalvorgänge durchgeführt. Ein wesentlicher Beitrag des Korrekturglieds wurde im Vergleich zu der totalen Phononleitfähigkeit oberhalb von 1 K gefunden.

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Résumé On a étudié, dans tout l'intervalle des températures comprises entre 0.2 et 4 K, le rôle des processus normaux à trois phonons dans l'analyse de la conductivité thermique du réseau de HD solide. L'étude s'est effectuée en calculant la contribution du terme de correction dû aux processus normaux à trois phonons, à la conductivité thermique totale du réseau de l'échantillon pur de HD solide, dans l'intervalle de températures considéré. On a, de même, effectué l'étude pour les différentes valeurs de la vitesse de relaxation de dispersion des processus normaux à trois phonons. On a trouvé une contribution considérable due au terme de correction comparé à la conductivité totale de phonon au-dessus d'1 K.

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0.2–4 . , , . . , 1 .

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The author wishes to express his thanks to Dr. R. A. Rashid, Dr. R. H. Misho and Dr. G. S. Verma for their interests in the present project.     

Naphthalintetrachloride

Zusammenfassung Die vier Naphthalintetrachloride vom Schmp. 182°, 116 bis 118°, 97 bis 98° und 132 bis 133° (- bis -I) sind Stereoisomere der 1,2,3,4-Reihe. -I wurde nach der Vorschrift vonFischer ¹, - und -I wurden nachRiemschneider ² hergestellt.     

The μ-and δ-opioid pharmacophore conformations of cyclic β-casomorphin analogues indicate docking of the Phe3 residue to different domains of the opioid receptors

Summary Cyclic -casomorphin analogues with a d-configured amino acid residue in position 2, such as Tyr-c[-Xaa-Phe-Pro-Gly-] and Tyr-c[-Xaa-Phe-d-Pro-Gly-] (Xaa=d-A₂bu, d-Orn, d-Lys) were found to bind to the -opioid receptor as well as to the -opioid receptor, whereas the corresponding l-Xaa² derivatives are nearly inactive at both. Low-energy conformers of both active and nearly inactive derivatives have been determined in a systematic conformational search or by molecular dynamics simulations using the TRIPOS force field. The obatained conformations were compared with regard to a model for -selective opiates developed by Brandt et al. [Drug Des. Discov., 10 (1993) 257]. Superpositions as well as electrostatic, lipophilic and hydrogen bonding similarities with the -opioid receptor pharmacophore conformation of t-Hpp-JOM-13 proposed by Mosberg et al. [J. Med. Chem., 37 (1994) 4371, 4384] were used to establish the probable -pharmacophoric cyclic -casomorphin conformations. These conformations were also compared with a -opioid agonist (SNC 80) and the highly potent antagonist naltrindole. These investigations led to a prediction of the -and -pharmacophore structures for the cyclic -casomorphins. Interestingly, for the inactive compounds such conformations could not be detected. The comparison between the -and -pharmacophore conformations of the cyclic -casomorphins demonstrates not only differences in spatial orientation of both aromatic groups, but also in the backbone conformations of the ring part. In particular, the differences in ² and ² (70°,-80°; 165°,55°) cause a completely different spatial arrangement of the cyclized peptide rings when all compounds are matched with regard to maximal spatial overlap of the tyrosine residue. Assuming that both the -and -pharmacophore conformations bind with the tyrosine residue in a similar orientation at the same transmembrane domain X of their receptors, the side chain of Phe³ as a second binding site has to dock with different domains.This paper is based on a presentation given at the 14th Molecular Graphics and Modelling Society Conference, held in Cairns, Australia, August 27–September 1, 1995.     

Effect of the solvent on selective hydrogenation of 6, 10-dimethylundeca-3,5,9-trien-2-one

Reaction mechanism for selective hydrogenation of pseudo-ionon on Raney-Ni in the presence of n- and iso-alcohols has been studied. From the analysis of ESR spectra, the dependence of selectivity on the solvent is concluded.

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- Ni- . .

     

The influence of pentaamminerhodium(III) on the1H n.m.r. spectra and pyrrole pKas of coordinated imidazoles and pyrazoles

Summary The following [(NH₃)₅RhLH]Cl₃ salts were preparedvia the [(NH₃)₅Rh(O₃SCF₃)](O₃SCF₃)₂ synthetic route; LH=1-methylimidazole (1CH₃imH), 2-methylimidazole (2CH₃imH), 4-methylimidazole (4CH₃imH), 5-methylimidazole(5CH₃imH), and pyrazole (pyzH). pK_a's at 25.0°C were determined for [(NH₃)₅RhLH]³⁺ complexes as follows: 2CH₃imH, 10.4±0.1; 5CH₃imH/4CH₃imH isomer mixture, 10.3±0.1; pyzH, 6.54±0.05. The influence on the pK_a's of imidazoles is dominated by withdrawal of the rhodium(III) centre and may be compensated by the presence of ring methylation by only 0.5log units for cobalt(III) and rhodium(III) derivatives, compared to 1.3 units for the -withdrawing ruthenium(III) centre. In the case of the -acceptor pyrazole ring, [(NH₃)₅Rh]³⁺ is observed to serve as a slight -donor and raises the pK_a above the cobalt(III) analogue. The¹H n.m.r. spectra of [(NH₃)₅RhLH]³⁺ complexes of the substituted imidazoles and pyrazole exhibit a deshielding order. C–2H>C–5H>C–4H for imidazoles and C–3H>C–5H>C–4H for pyrazole, as do their cobalt(III) analogues. The magnitude of values (=_{free L}-_complex) are virtually the same as in the cobalt(III) systems which shows that TIP influences are unimportant compared to ring rehybridization in estabilishing chemical shifts for both the cobalt(III) and rhodium(III) complexes. The imidazolato and pyrazolato complexes exhibit resonances upfield of the respective substituted imidazole or pyrazole complex in keeping with more negative charge on the rings; the influence is largest at C–2H of imidazolates and C–3H of pyrazolate.     

Carbon-13NMR spectra of isomeric diazaphenanthrenes,II δ-Effects in sterically crowded methyl derivatives

Steric downfield shifts due to a -CH moiety and a -nitrogen lone pair are similar in methylated diazaphenanthrenes. Most probably steric distortions are responsible for the -effects observed, and this might be quoted as a further evidence for a nearly equal steric requirement of a hydrogen atom and a nitrogen lone pair.

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C-13 NMR-Spektren isomerer Diazaphenanthrene, II. -Effekte in sterisch gehinderten Methylderivaten

Zusammenfassung Sterisch bedingte Tieffeldverschiebungen infolge von -CH-Molekülteilen und -lone pairs von Stickstoffatomen sind in methylierten Diazaphenanthrenen ähnlich. Die gemessenen -Effekte dürften auf sterische Deformationen zurückzuführen sein, was als weiteres Indiz für den nahezu gleichgroßen Raumbedarf eines Wasserstoffatoms und eines freien Elektronenpaars am Stickstoff gewertet werden kann.

     

Lattice Dynamics in LaTa2-2xNb2xVO9-δ (x=0–0.1) Solid Solutions

The oxygen nonstoichiometry (x) of LaTa_2-2xNb_2xVO₉- (x = 0–0.1) solid solutions was studied using Xray phase analysis, vibrational spectroscopy, and radiospectroscopy. A correlation was found between (x) and the unit cell volume V(x) of the solid solutions. It was shown that the infrared spectra of LaTa₂VO₉- change in passing from = 0 to 0. The structural position of the oxygen vacancy in LaTa_2-2xNb_2xVO₉- is discussed.     

Synthesis of δ-alkoxy-α, α-dicarbonyl-substituted dienes and study of their valence isomerization

Methods of synthesis of dienic -alkoxy-, -dicarbonyl-substituted compounds were experimentally examined. The structure of the synthesized compounds was studied by¹H and¹³C-NMR methods. It was shown that the -alkoxy diesters are present in equilibrium with 2H-pyrans, while -alkoxy--methyl diesters and 2-(3-alkoxypropen-2-ylindene)indanediones exist in an open form and do not undergo cyclization into 2H-pyrans.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2561–2565, November, 1990.     

IR study of isopropanol adsorption on haematite

The IR study shows that isopropanol interacts with haematite at IR beam temperature both as a physisorbed form, hydrogen bonded to basic sites of the surface, and as isopropoxide groups. At 423 K a decomposition of isopropoxide groups produces enolate anions of acetone.

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, , - , . 150 °C .

     

An inequality for 3D database searching and its use in evaluating the treatment of conformational flexibility

Summary A mathematical formula is introduced for predicting the number of hits that should be observed in a flexible 3D database search, based on the results of a set of related queries. The projected number of hits is always greater than or equal to the actual number of hits, the discrepancy being due to imperfect treatment of conformational flexibility of the molecules. Hence, the difference between the projected and actual number of hits, , serves to measure how well conformational flexibility is being treated, in a manner that is objective, easy for a user to quickly verify, and independent of the particular algorithm for flexible 3D database search. It is shown that is a function both of how well conformational flexibility is treated and of the precision of the query. When the distance constraint is defined only to a precision of ±2.0 Å, in a single-conformer database of drug-like molecules values of only 0.03 are found, while in a single-conformer database of di- and tripeptides, is 0.15. At increased precision, a flexible 3D database search becomes critical. For a single-conformer database, using a query of precision ±0.2 Å, applied to a database of drug-like molecules, is 0.97; applied to a database of di- and tripeptides, is 2.21. By contrast, treating conformational flexibility by storing up to 100 conformers per molecule, at this precision, applied to a database of drug-like molecules, is 0.002; applied to a database of di- and tripeptides, is 0.07. This inequality, and hence , is defined only for database queries containing a single distance constraint; how the inequality may generalize to higher-dimensional queries is still unclear.     

Transformed steroids. 121. Synthesis of the δ-lactone of 3β-acetoxy-16α-hydroxy-6-oxo-24-nor-5α-chol-17(20)-en-23-oic acid

The synthesis of the ¹⁷⁽²⁰⁾-16 analog of natural chiogralactone is described. Attempts to introduce a 6-oxo group directly into the -lactone proved unsuccessful, since the first stage — saponification — took place with the formation of three products: the 3-hydroxy--lactone, the 3-hydroxy-²⁰⁽²²⁾-lactone, and the 15,17(20)-dienoic acid. The synthesis of the desired compound was effected from the ethyl ester of the 5,16-dienoic acid by the scheme 3-acetate3-tosylate6-hydroxy-3,5-cyclosteroid6-oxo-3,5-cyclosteroid6-oxo-5H--lactone. It has been shown that the cyclopropane ring in the 3,5-cyclosteroid -lactone is extremely stable under the conditions of acid treatments.N. D. Zelinskii Institute of Organic Chemistry, Academy of Sciences of the USSR, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 184–187, March–April, 1981.     

Transformed steroids 117. Synthesis of 5α-hydroxy-6-oxosteroids with a δ-lactone ring E

The paper is devoted to the synthesis of steroidal 5-hydroxy-6-oxolactones from ethyl esters of 5,6-dienic acids. By epoxidating the latter it has been shown that, in addition to the usual formation of 5,6-oxides, opening of the 16, 17-oxide ring initially formed takes place and this is accompanied by intramolecular cyclization to a 17,20-dihydroxy--lactone. The trans-opening of the 5,6-epoxide in the epoxy--lactone and subsequent oxidation with N-bromosuccinimide has led to a new representative of steroidal -lactones — the 23,16--lactone of the 3-acetate of 3, 5, 16, 17, 20-pentahydroxy-6-oxo-24-norcholan-23-oic acid.N. D. Zelinskii Institute of Organic Chemistry, Academy of Sciences of the USSR, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 208–213, March–April, 1980.     

Synthesis and structure of 1-benzoyl-2,5-dimethyl- and 1,2,5-trimethyl-4-arylpiperideins

Isomeric 1-benzoyl-2,5-dimethyl-³-piperidein and 1-benzoyl-2,5-dimethyl-⁴-piperidein were prepared from disubstituted -piperidols and were hydroxylated with osmium tetroxide. The isomeric 1,2,5-trimethyl-4-(p-nitrophenyl)-³- and-⁴-piperideins were obtained from trisubstituted -piperidols.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1200–1206, September, 1986.In conclusion, the authors would like to thank Yu. T. Struchkov and N. I. Lebedev for carrying out the x-ray structural study.