An energy decomposition analysis of intermolecular interactions

Within the context of extended geminal models the concepts of charge centroids and charge ellipsoids of the geminal one-electron densities, and an energy decomposition of the intermolecular potential, are introduced as tools of analysis. The intermolecular potential can within this framework be written as a sum of the distortion energies of the subsystems and the interaction energies between the distorted subsystems. The interaction energy is further partitioned into a Coulombic, exchange and correlation contribution. Three classes of complexes are studied: hydrogen bonded systems (HF)₂, H₂OHF, (H₂O)₂; strongly bonded electron donor-acceptor (EDA) complexes: BH₃NH₃, BH₃CO; and weakly bonded EDA complexes: F₂NH₃, Cl₂NH₃ and ClFNH₃. The main results of the calculations, using basis sets consisting of [9s, 6p, 2d](Cl), [7s, 4p, 2d] (B, N, O, F), [4s, 2p](H) contracted Gaussian-type functions, and the numerical models EXRHF3 and EXGEM7, are as follows. The bonding in these complexes is essentially due to a lone pair of the donor subsystems approaching the vacant space in the vicinity of a nucleus of the acceptor system. The interaction energy is therefore dominated by the Coulombic term. However, the sum of the distortion terms is larger than the magnitude of the Coulombic term. Hence, the exchange and correlation terms give a substantial contribution to the intermolecular potential. If the components of the decomposition of the potential are resealed by using the magnitude of the interaction energy as the energy unit, a remarkable similarity between the three classes of complexes is disclosed.     

Comparison of chromatographic ion-exchange resins IV. Strong and weak cation-exchange resins and heparin resins

A comparative study was performed on heparin resins and strong and weak cation exchangers to investigate the pH dependence, efficiency, binding strength, particle size distribution, static and dynamic capacity, and scanning electron microscopy pictures of chromatographic resins. The resins tested include: Heparin Sepharose FF, SP Sepharose FF, CM Sepharose FF, Heparin Toyopearl 650 m, SP Toyopearl 650 m, CM Toyopearl 650 m, Ceramic Heparin HyperD M, Ceramic S HyperD 20, and Ceramic CM HyperD F. Testing was performed with four different proteins: anti-FVII Mab (IgG), aprotinin, lysozyme, and myoglobin. Dependence of pH on retention was generally very low for proteins with high isoelectric point (pI), though some decrease of retention with increasing pH was observed for CM Ceramic HyperD F and S Ceramic HyperD 20. Binding of anti-FVII Mab with pI < 7.5 was observed on several resins at pH 7.5. Efficiency results show the expected trend of increasing dependence of the plate height with increasing flow rate of Ceramic HyperD resins followed by Toyopearl 650 m resins and the highest flow dependence of the Sepharose FF resins corresponding to their pressure resistance. Determination of particle size distribution by two independent methods, coulter counting and SEM, was in good agreement. Binding strength of cation-exchange resins as a function of ionic strength varies depending on the protein. Binding and elution at high salt concentration may be performed with Ceramic HyperD resins, while binding and elution at low salt concentration may be performed with model proteins on heparin resins. Employing proteins with specific affinity for heparin, a much stronger binding is observed, however, some cation exchangers may still be good substitutions for heparin resins. Dynamic capacity at 10% breakthrough compared to static capacity measurements and dynamic capacity displays that approximately 40-80% of the total available capacity is utilized during chromatographic operation depending on flow rate. A general good agreement was obtained between results of this study and data obtained by others. Results of this study may be used in the selection of resins for testing during protein purification process development.     

Papierchromatographische Trennung des Galliums von Eisen,Titan und Aluminium und seine fluorometrische Bestimmung mit 5,7-Dibrom-8-hydroxychinolin

Zusammenfassung Mit dem Lösungsmittelgemisch Butanol-Eisessig-Acetessigester-Wasser gelang nach einer Laufzeit von 40 Stunden eine vollkommene Trennung des Galliums von der mehrfachen Menge Eisen, Aluminium und Titan. Die anschließend versuchte quantitative Bestimmung des Galliums stieß auf Schwierigkeiten, da das verwendete Chromatographierpapier Spuren von Eisen und Kupfer enthielt. Daher wurde die fluorometrische Bestimmungsmethode für Gallium mit 5,7-Dibrom-8-hydroxychinolin so umgestaltet, daß die Bestimmung des Galliums auch in Gegenwart kleiner Eisen- und Kupfermengen möglich ist. Schließlich wird ein Analysengang für die Galliumbestimmung in Lösungen angegeben, die die tausendfache Menge an Eisen und Aluminium enthalten.

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Summary Complete separation of gallium from several times as much iron, aluminium, and titanium was obtained by treating the mixture with a mixed solvent, made up of butanol, glacial acetic acid, acetic ester, water, for 40 hours. The subsequent attempts to make a quantitative determination of the gallium encountered difficulties because the chromatographing paper used contained traces of iron and copper. Accordingly, the fluorometric method for determining gallium with 5,7-dibromo-8-hydroxyquinoline was modified in such manner that gallium could be determined even when small quantities of iron and copper are present. Finally, a scheme is given for determining gallium in solutions, which contain a thousand times the quantity of iron and aluminium.

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Résumé Il a été possible d'effectuer en 40 heures une séparation complète du gallium de quantités plusieurs fois supérieures de fer, d'aluminium et de titane à l'aide d'un mélange de solvants butanol-acide acétique-ester acetylacétique-eau. Les essais de dosage consécutif du gallium se sont heurtés à des difficultés résultant du fait que le papier employé pour la chromatographie contenait des traces de fer et de cuivre. En conséquence on a modifié la méthode de dosage fluorométrique du gallium à l'aide de la 5,7-dibromo-8-hydroxyquinoléine pour permettre son application en présence de petites quantités de fer et de cuivre. En définitive, on donne un protocole de dosage du gallium dans des solutions qui contiennent des quantités de fer et d'aluminium mille fois supérieures.

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Herrn Prof. Dr.Robert Strebinger zum 70. Geburtstag gewidmet.     

Zur manometrischen Mikrobestimmung des Kohlenstoffs und Wasserstoffs in organischen Verbindungen

Zusammenfassung Eine manometrische Mikrobestimmungsmethode für Kohlenstoff und Wasserstoff in organischen Verbindungen wurde ausgearbeitet. Die Verbrennung der Substanz erfolgt im Stickstoffstrom unter Zusatz einer bestimmten Menge Sauerstoff. Zur Oxydation noch unverbrannter Substanzdämpfe dient eine auf 750° C erhitzte, 16 cm lange Katalysatorschicht aus einem Gemisch von Kupfer- und Kobaltoxid. Wasser und Kohlendioxid werden in zwei Kühlfallen mit Kohlensäureschnee bzw. flüssiger Luft ausgefroren und anschließend in zwei evakuierte Quecksilbermanometer gleichzeitig verdampft. Aus den Druckzunahmen berechnet man den Kohlenstoff- und Wasserstoffgehalt der analysierten Substanz. Die Bestimmungsmethode ist universell anwendbar, wie die Analysenergebnisse von Verbindungen verschiedenster Zusammensetzung und unterschiedlichen Verhaltens zeigen. Eine vollständige Analyse beansprucht zirka 20 Minuten. Die Analysenresultate einer Testsubstanz wurden statistisch ausgewertet. Bei einer vorgegebenen statistischen SicherheitS von 95% betragen die Streubereiche ±x für die Kohlenstoffwerte ±x _C =0,42% und für die Wasserstoffwerte ±x_H = ±0,27%.

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Summary A method has been worked out for the manometric microdetermination of carbon and hydrogen in organic compounds. The sample is burned in a stream of nitrogen with the addition of a certain amount of oxygen. The still unburned vapors from the sample are oxidized by means of a layer of catalyst consisting of a mixture of copper-and cobalt oxide and heated to 750° C. Water and carbon dioxide are frozen out in two cooling vessels surrounded by solid carbon dioxide and liquid air respectively and subsequently volatilized simultaneously into two evacuated mercury manometers. The carbon and hydrogen content of the sample are determined from the increases in pressure. The procedure is applicable in all cases as shown by the analytical data obtained from compounds with most varied compositions and varied behaviour. A complete analysis consumes about 20 minutes. The analytical results from a test substance were evaluated statistically. With an accepted accuracyS of 95%, the deviation ranges ±x for the carbon contents are ±x_C = 0.42% and for the hydrogen values ±x_H = ±0.27%.

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Résumé On a mis au point une méthode manométrique pour le microdosage du carbone et de l'hydrogène dans les composés organiques. La combustion de la substance s'effectue sous courant d'azote, additionné d'une quantité déterminée d'oxygène. Pour oxyder les vapeurs de la substance qui n'a pas encore brûlé, on utilise une couche de catalyseur, longue de 16 cm, chauffée à 750° C et composée d'un mélange d'oxydes de cuivre et de cobalt. On condense l'eau et le gaz carbonique dans deux pièges refroidis par de la neige carbonique ou par de l'air liquide, et, pour finir, on les vaporise simultanément dans deux manomètres à mercure où l'on a fait le vide. A partir de l'augmentation de pression, on calcule la teneur en carbone et en hydrogène de la substance analysée. La méthode de dosage est universellement applicable, comme le montrent les résultats d'analyse de composés de diverses compositions et de propriétés différentes. Une analyse complète demande environ 20 minutes. On a utilisé statistiquement les résultats d'analyse d'une substance étalon. En comptant sur une limite de confianceS, statistiquement de 95%, les domaines de dispersion ±x atteignent ±x_C = 0,42% pour les valeurs du carbone et ±x_H = 0,27% pour les valeurs de l'hydrogène.

     

PPh3Me[MoBr5(CH3CN)]. IR-Spektrum,magnetisches Verhalten und Kristallstruktur

PPh₃Me[MoBr₅(CH₃CN)]. I.R. Spectrum, Magnetic Behaviour, and Crystal Structure Molybdenum tetrabromide and acetonitrile form MoBr₄(CH₃CN)₂, from which PPh₃Me[MoBr₅(CH₃CN)] is obtained by reaction with PPh₃MeBr in dibromo methane. Both compounds are characterized by their IR spectra. By evaluation of the magnetic susceptibility of PPh₃Me[MoBr₅(CH₃CN)] in the temperature range of 4.2 to 290 K the Curie-Weiss parameters μ_cw = 2.65 B.M. and Θ = ?44 K were obtained. The crystal structure of PPh₃Me[MoBr₅(CH₃CN)] was determined by X-ray diffraction (2426 observed reflexions, R = 0.082). Crystal data: a = 1064.9, b = 2172.1, c = 1330.4 pm, β = 119.92º, space group P2₁/c, Z = 4. In the crystal, PPh₃Me⁺ and [MoBr₅(CH₃CN)]^? ions are packed in alternate cation and anion layers perpendicular to a. In the anion the Mo atom has a distorted octahedral coordination. The bond length of the bromine atom in trans position to the N atom is considerably shorter than the other MoBr distances.     

On weak convergence to Brownian motion

Summary We consider a minimal form of the usual conditions for the dependent central limit theorem and invariance principle for near martingales. We show that these conditions imply convergence to Brownian motion in a way that is slightly stronger than weak convergence in D[0,). On the other hand, if a sequence of processes with paths in D[0,) converges to Brownian motion in this way, then we can always find a sequence of partitions of the time axis that is such that these conditions hold for the corresponding array of increments.     

Absorptionsspektrographische Studien an l-Ascorbinsäure I

Ohne ZusammenfassungMit 9 Abbildungen.Vgl. hierzuE. Schauenstein, Chemie56, 156 (1943) bzw.R. Czmiel, W. Halden undE. Schauenstein, Naturwiss.30, 586 (1942). — Eine Zusammenfassung der vorliegenden Arbeit erschien bereits in dieser Zeitschrift [Mh. Chem.78, 415 (1948)] als vorläufige Mitteilung.     

A quartz crystal microbalance study of the adsorption of asphaltenes and resins onto a hydrophilic surface

The adsorption of extracted and purified samples of asphaltenes and resins onto gold surfaces has been studied as a function of bulk concentration using a quartz crystal microbalance with dissipation measurements (QCM-D). With this device, which works equally well in transparent, opaque, and nontransparent samples, the adsorbed amount is measured through a change in resonant frequency of the quartz oscillator. The measured change in dissipation reports on changes in layer viscoelasticity and slip of the solvent at the surface. The results show that the adsorbed amount for resins from heptane corresponds to a rigidly attached monolayer. The adsorbed amount decreases with increasing amount of toluene in the solvent and is virtually zero in pure toluene. Asphaltenes, on the other hand, adsorb in large quantities and the mass and dissipation data demonstrate the presence of aggregates on the surface. The aggregates are firmly attached and cannot be removed by addition of resins. On the other hand, resins and asphaltenes associate in bulk liquid and the adsorption from mixtures containing both resins and asphaltenes is markedly different from that obtained from the pure components. Hence, we conclude that preformed resin aggregates adsorb to the surface. These results are compared and discussed in relation to adsorption from crude oil diluted in heptane/toluene mixtures.