Orbital correlation effects: The independent pair-potential approximation with application to the ground state and first ionized state of boron hydride

A new method is proposed for calculating correlation effects in atomic and molecular systems. The basis of the method is the formulation of a set of partial configuration expansions which yield directly variational orbital correlation corrections which are appropriately summed in order to obtain an estimate of the total correlation energy. This method is applied to the ground state of boron hydride and its cation at the equilibrium distance of BH. The results of the method are compared in detail with independent electron pair results and second order CI results. It is further shown that multiple substitutions are approximately accounted for in this method and the extent to which they are included is compared with other approximations. Finally, three methods of increasing accuracy, aimed at reducing the necessary computational effort, are given for determining the vertical ionization potential. The most economical method yields an IP of 9.70 eV or 0.03 eV less than the experimental IP. Completion of the basis is estimated to improve this value to 9.77 eV.     

Formation and Crystal Structure of [(F5TeOXe)+·SO2ClF][Sb(OTeF5)6-]

Xe(OTeF₅)₂ reacts with Sb(OTeF₅)₃ under the formation of [Xe₂(OTeF₅)₃]⁺[Sb(OTeF₅)₆]^-. From SO₂ClF solution a yellow solvate [F₅TeOXe]⁺·SO₂ClF· [Sb(OTeF₅)₆]^- is formed with the crystal data: a = 1028.1(1), b = 1040.9(1), c = 1780.2(3) pm, α = 98.07(1), β = 97.68(1), γ = 105.82(1)°, space group . The O-Xe···O fragment is essentially linear (176.1(2)°), and the two Xe-O distances are quite different 197.1(4) and 242.6(4) pm.     

Synthesis of new 1,3-bis（phenylethynyl）disilazanes

Three new 1,3-bis(phenylethynyl)disilazanes were synthesized from the reaction of 1,3-dichlorodisilazanes with (phenylethy- nyl)lithium,and characterized by infrared (IR) spectra,nuclear magnetic resonance (NMR) and mass spectrometry (MS).     

Theoretical formalism and experimental verification of line shapes of NMR intermolecular multiple-quantum coherence spectra

Although the theories and potential applications of intermolecular multiple-quantum coherences (iMQCs) have been under active investigations for over a decade, discussion of iMQC NMR signal formation was mainly confined in the time domain. In this paper, a full line-shape theory was developed to describe iMQC signals in the frequency domain. Relevant features of the line shape, such as peak height, linewidth, and phase, were investigated in detail. Predictions based on the theory agree well with experimental and simulated results. Since radiation-damping effects always couple with iMQCs in highly polarized liquid-state NMR systems, and strongly radiation-damped signals have many spectral characteristics similar to those of iMQCs, a detailed comparison was also made between them from different spectral aspects. With detailed comparison of peak height, linewidth, and phase, this work demonstrates that the iMQC and radiation-damping phenomena result from two completely different physical mechanisms despite that both present similar signal features and coexist in highly polarized liquid-state NMR systems.     

An indirect flame emission spectrometry method for the determination of traces of sulphur. I

Summary An accurate and simple indirect method of flame emission spectrometric determination of small quantities of elemental sulphur is described. The method is based on the reduction of elemental sulphur by means of sodium borohydride and oxidation of the resulting boron-sulphur compounds to sulphate by means of hydrogen peroxide. The determinations can be carried out in the presence of methanol, acetone, dimethylformamide, toluene and benzene. The detection limit of the reported method is 1 ppm of sulphur.

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Indirekte etnissionsspektroskopische Bestimmungsmethode für Spuren elementaren Schwefels. I.

Zusammenfassung Eine genaue und einfache, indirekte, emissionsspektroskopische Methode zur Bestimmung geringer Mengen elementaren Schwefels wurde ausgearbeitet. Sie besteht in der Reduktion des elementaren Schwefels mit Hilfe von Natriumborhydrid und in der Oxydation der entstehenden Bor-Schwefel-Verbindung zu Sulfat mit Hilfe von Wasserstoffperoxid. Die Analyse wurde in Methanol, Aceton, Dimethylformamid, Toluol und Benzol durchgeführt. Die Erfassungsgrenze beträgt 1 ppm Schwefel.

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Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980.     

The effect of the mechanical properties of the molecular network on the wool-water isotherm

Summary The present position of theoretical investigation of the water-content versus relative humidity isotherm is briefly indicated. Previous workers have anticipated an effect on equilibrium water-content arising from the mechanical properties of the keratin network. Such an effect is reported for supercontracted wool fibres and for reduced and S-methylated fibres, for which an increased saturation water-content is observed. In the case of S-methyl wool, saturation water-content shows little or no dependence on the number of disulphide cross-links, however it does depend on the number of S-methyl groups present. The results are considered in terms ofFlory-Huggins solution theory, and it is indicated that this theory can be usefully applied for relative humidities in excess of 85%. In normal wool solution absorption is permitted only in the noncrystalline component, but in supercontracted wool or S-methyl wool takes place in both components. Even when saturation water-content is greatly increased the isotherm is not appreciably changed below 85% R. H., indicating that no additional sites for strong binding of water become available; apparently all such sites are accessible in normal wool at approximately 85% relative humidity.

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Zusammenfassung Der gegenwärtige Stand theoretischer Untersuchungen für den isothermen Wassergehalt gegen relative Feuchtigkeit ist kurz kritisch dargelegt. Die bisherigen Bearbeiter haben einen Einfluß auf das Gleichgewicht des Wassergehaltes seitens der mechanischen Eigenschaften des Keratinnetzwerkes angenommen. Ein solcher Effekt wird für superkontrahierte Wollfasern und für solche, reduziert und mit Schwefelmethyl behandelt, mitgeteilt, für die eine erhöhte Wassersättigung zu beobachten ist. Im Fall der schwefelmethylierten Wolle zeigt die Sättigung geringe oder keine Abhängigkeit von der Zahl der Disulfidvernetzungen, sie hängt jedoch von der Zahl der Schwefel-Methylgruppen ab. Diese Resultate werden mit derFlory-Huggins-Lösungstheorie betrachtet, und es zeigt sich, daß diese Theorie gut für relative Feuchtigkeiten größer als 85% angewendet werden kann. In normaler Wolle ist Lösungsabsorption nur in den nichtkristallinen Anteilen möglich, aber in superkontrahierter oder schwefelmethylierter Wolle findet sie auch in den Kristalliten statt. Auch wenn der Sättigungswert der Isotherme gegen Ende stark beeinflußt wird, ändert sich der Verlauf der Isotherme unterhalb 85% r. F. nicht. Das zeigt, daß kerne zusätzlichen Plätze für starke Wasserbindungen entstehen. Offensichtlich sind alle diese Plätze in normaler Wolle bei etwa 85% r. F. zugänglich.

     

Charge influence in semi-empirical calculations of heteroatomic ionic and neutral molecules

Iterative extended Hükel calculations for all valence electrons and iterative PPP calculations in the variable electronegativity formalism for -electrons were performed on benzene, pyridine, fluorobenzene, and the pyrylium ion. The charge distributions for all compounds were found more uniform and plausible with the iteration procedures than without. Polarization effects from the-electrons were found to be of importance for the -electrons. The lone-pair picture of the highest occupied MO in pyridine is preserved in the iterative extended Hückel method, and two lone-pairs were obtained on the fluorine atom of fluorobenzene. The results indicate that this atom is not hybridized.

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Zusammenfassung Benzol, Pyridin, Fluorbenzol und Pyriliumion wurden mit einer iterativen EH-Methode und einer iterativen PPP-VE-Methode berechnet. Es zeigte sich, daß Ladungsverteilungen bei Benutzung des Iterationsverfahrens besser beschrieben werden. Polarisationseffekte der-Elektronen auf die -Elektronen stellen sich als wichtig heraus. Auch in der IEH-Methode bleibt das oberste besetzte MO des Pyridins ein einsames Elektronenpaar. Am Fluoratom im Fluorbenzol werden zwei einsame-Elektronenpaare erhalten. Die Resultate führen zu der Annahme, daß dieses Atom nicht hybridisiert ist.

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Resumé Des calculs par les méthodes itératives de Hückel étendu pour tous les électrons de valence et de PPP avec électronégativité variable pour les électrons ont été effectués pour le benzène, la pyridine, le fluorobenzène et l'ion pyrylium. Les distributions de charge pour tons ces composés sont plus uniformes et plus plausibles avec les procédés itératis que sans. Les électrons ont un effet de polarisation important sur les électrons . La plus haute orbitale occupée dans la pyridine reste identifiable comme la paire libre dans la méthode de Hückel étendue, et l'on obtient deux paires libres sur l'atome de fluor du fluorobenzène. Cet atome n'est pas hybride.

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Sponsored in part by King Gustaf VI Adolfs 70-Years Fund for Swedish Culture, Knut and Alice Wallenberg's Foundation, and in part by the Swedish National Research Council.     

Beiträge zur Chemie der Alkylverbindungen von Übergangsmetallen. XLIV. Tetrakis(alkoxycarbonylmethyl)titan-Verbindungen

Contributions to the Chemistry of Transition Metal Alkyl Compounds. XLIII. Tetrakis(alkoxycarbonylmethyl)titanium Compounds Organotitanium(IV) compounds of the type (ROCOCH₂)₄Ti (R ? C₂H₅, i-C₃H₇, t-C₄H₉, C₆H₅, C₆H₅CH₂) were obtained by reactions of ROCOCH₂Li derivatives with TiCl₄ at low temperature. The compounds which decompose only above 90°C were characterized by the hydrolysis products, anaerobic reactions with iodine, and the i.r. spectra. The bond conditions are discussed.     

On the determination of polarity parameters of silica by means of solvatochromic probe dyes

Empirical solvent parameters of silica surfaces are determined by means of solvatochromic dyes, e.g., Cu(tmen) (acac)⁺ ClO ₄ ^– /B(C₆H₅) ₄ ^– , Fe(phen)₂(CN)₂, and Michlers Ketone dissolved in 1,2-dichloroethane or cyclohexane. The values obtained by UV/VIS-measurements are compared with both the polarity scales of Kamlet and Taft and with Gutmann's donor and acceptor numbers. Kamlet and Taft's -parameter (the hydrogen-bond donation capacity of a solvent) is determined independently by means of salicylideneaniline. The ^* of silica is determined using 5-N,N-dimethylamino-5-nitro-2,2-bithiophene and the complex of tetracyanoethylene with Michlers Ketone, respectively. Further on the reliabilities of the obtained Kamlet-Taft parameters , , and ^* are checked by comparism with experimental and calculated values of theE _T(30)-parameter of silica by means of multi-parameter regression analysis. The surface properties of silica are influenced mainly by HBD-properties (75%) and dipolarity/polarizability ^* (20%), but hardly by the HBA-properties (<5%). UV/VIS-measurements were carried out in a special equipment with glass fiber optics, A drawing of the apparatus is given.