Total chromatographic optimization (TOCO) II. Precision and efficiency of analysis

Summary A chromatographic system set at an operating condition takes its own precision and efficiency which are numerically described by the information called FUMI and the information flow , respectively. Optimization for a variable such as mobile phase composition draws a line in the - space. This paper demonstrates that optimization of different variables displays different patterns of lines in the - space. The variables examined here are mobile phase composition, column length, flow rate (velocity) and detection wavelength (or the amount of internal standard). Clear difference in the analytical roles of the variables can be known from the - plots.     

Improvement of Solubility and Dissolution of 19-Norprogesterone via Inclusion Complexation

In an effort to modify the solubility and dissolution rate of the contraceptive steroid, 19-norprogesterone in order to improve its bioavailability, the cyclodextrin complexation approach was chosen. In solution, the complex formation with -cyclodextrin (-CD), hydroxyethyl -cyclodextrin (HE--CD) and hydroxypropyl -cyclodextrin (HP--CD) was confirmed by using solubility, UV, IR and ¹H-NMR spectrophotometric techniques. The phase solubility diagrams were categorized as A_L-type. The complexing affinity of the CDs investigated were ranked as follows: -CD > HP--CD > HE--CD. The complexation thermodynamic parameters were obtained from the temperature dependence of the dissociation constants. In the solid state, differential scanning calorimetery (DSC) and optical microscopy methods were utilized to characterize the complexes. Dissolution studies showed that such molecularly encapsulated forms offered a marked improvement in the dissolution rate compared to the parent drug.     

Recent progress in tartaric acid‐modified Raney nickel system for enantio‐differentiating hydrogenation

Tartaric acidmodified Raney nickel (TAMRNi) is an enantiodifferentiating catalyst for hydrogenation of ketones. The stereochemical models explaining the enantiodifferentiation of ketoester and 2alkanone were unified as an extended stereochemical model by the experimental supports. Based on this new model, a working hypothesis to improve the enantiomeric excess (ee) of the ketoester/TAMRNi system was developed, and the ee was improved to 96%. By further fine tuning of this system, almost perfect enantiodifferentiation resulting in over 98% ee was achieved.     

Theoretical Study of the Products of Acetylene Addition to HgCl2

The ab initio MP2 method is used with the LANL2DZ basis to calculate the mercury chloride ,-complex with two acetylene molecules (1) and various isomeric forms of mercury di()-vinyl chloride -complexes (2): cis-cis (2A), cis-trans (2B), and trans-trans (2C). The ,-complex is the most stable form of all those considered; the difference between 1 and 2A is 24.9 kcal/mole. A relation between the total energies (kcal/mole) for isomeric forms 2 is established to be 2A (0) < 2B (0.98) < 2C (1.58). Complex 1 is shown to be transformed into 2A via the intermediate formation of 3, which is a hybrid form of the complex (,-complex of mercury chloride with two acetylene molecules). The structures of the transition states for the transformations of 1 into 3 (structure 4) and of 3 into 2A (structure 5) and the corresponding transition activation energies are determined. The interaction of 2A, 2B, and 2C with the Cl^- anion as a model nucleophile is considered. It is shown that the resulting anions (6A, 6B, 6C) have a planar structure with the relative stability increasing in the series 6A<6B<6C.     

A New Relation Between the Maxima Conductivities of Nonaqueous Concentrated Electrolytes and Chemical Hardness of Solvents and Salts

For nonaqueous electrolytes, using the HSAB principle, we tried to correlate the conductivity maxima _MAX, vs. only two intrinsic parameters: chemical hardness of the solvent and that of the salt. Thus, not only the nature of the solvent but also that of the salt were taken into account. We were able to predict for a given solvent the variation of _MAX as a function of the hardness of the salt and that of the solvent: _MAX = K(1 – ||/_SOLVENT) with || = |_SOLVENT – _SALT| and K a constant in S-cm^–1 independent of the salt, but not of the solvent.     

3, 3, 3-Trifluoropropyl(methyl)cyclosiloxanes

The catalytic rearrangement of the cyclopentasiloxanes _mD_5-m, where represents a 3, 3, 3-trifluoropropyl(methyl)siloxane link and D a dimethylsiloxane link, and m=2–5 has been studied by the method described previously [1]. The rate of rearrangement and the rate of formation of a linear polysiloxane rise with an increase in m from 2 to 4. The equilibrium concentration of the linear polysiloxane formed from _mD_5-m and from _mD_4-m (m=0–4) [1] is inversely proportional to the molar fraction of links in the ring and rises with an increase in the total concentration of siloxane links in solution. Results have been obtained on the kinetics of the formation of the cyclosiloxanes _mD_n (where m=0–5, n=0–5, and m+n=3-6) during the rearrangement of the cyclopentasiloxanes _mD_5-m. It has been established that at equilibrium a mixture of cyclosiloxanes _mD_n containing practically constant ratios of tetramers, pentamers, and hexamers (m+n=4, 5, and 6) is obtained, regardless of the composition and structure of the initial cyclosiloxane and of the conditions of rearrangement (polymerization). The cyclopentasiloxanes _mD_5-m are less active in the process of rearrangement than the cyclotetrasiloxanes _mD_4-m. The activity of the cyclosiloxanes in rearrangement in the presence of a base rises in the sequence D₄D_{3 2}D₃<₃D₂<₄D < ₂D₂ < ₃D.For part II, see [1].     

VUV-Photolyse von Methanol bei 1236 Å

Zusammenfassung Es wird über die indirekte und die direkte VUV-Photolyse von luftfreiem Methanol in flüssiger Phase bei 1236 Å berichtet. Bei der Bestrahlung von wäßr. 0,01m-Methanol wurden folgende Produkte und Ausbeuten erhalten: (H₂)=1,00, (HCHO)=0,27, (CH₂OH)₂=0,12, (CH₂OH·CHO)=0,04 und (HCOOH)=0,02. Die Photolyse von flüssigem Methanol lieferte die gleichen Produkte, jedoch mit höheren Ausbeuten: (H₂)=1,50, (HCHO)=0,98, (CH₂OH)₂=0,28 und (CH₂OH·CHO)=0,06. Unter Anwendung von Methanol als Radikalfänger konnte auch die Quantenausbeute der Wasserphotolyse bei 1236 Å, (H,OH)=1,025 verifiziert werden. Wahrscheinliche Reaktionsmechanismen werden diskutiert.

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V.U.V.-Photolysis of methanol at 1236 Å

The indirect and the direct v.u.v.-photolysis of air free methanol in liquid phase at 1236 Å is reported. After irradiation of aqueous 0.01M-methanol the following products were obtained: (H₂)=1.00, (HCHO)=0.27, (CH₂OH)₂=0.12, (CH₂OH·CHO)=0.04 and (HCOOH)=0.02. The photolysis of liquid methanol yielded the same compounds, however with higher amount as follows: (H₂)=1.50, (HCHO)=0.98, (CH₂OH)₂=0.28 and (CH₂OH·CHO)=0.06. Using methanol as a scavenger for the H and OH radicals the quantum yield of the water photolysis at 1236 Å could be verified to be (H,OH)=1.025. Probable reaction mechanisms are discussed.

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Mit 3 Abbildungen

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Herrn Prof. Dr.E. Broda zum 60. Geburtstag gewidmet.     

Triterpene Glycosides of Astragalus and Their Genins. LXI. Occurrence of Cycloartane 6-O-Monodesmosides

Cyclosiversigenin 6-O--L-rhamnopyranoside and 6-O--D-glucopyranoside were isolated fromAstragalus coluteocarpusBoiss. (Leguminosae) andAstragalus dissectusB. Fedtsch. et N. Ivanova, respectively. Cyclosiversigenin 5-O--L-rhamnopyranoside was shown to be an artifact forAstragalus coluteocarpus.Thus, the cyclosiversigenin 6-O--D-glucopyranoside that was isolated from certainAstragalusspecies is hypothesized also to be an artifact. Glycosylation of the 6 -hydroxyl group of cycloartanes by D-glucose and D-xylose, in contrast with other substituents, does not change the low-field position of the PMR signal of the 4-CH ₃ group (1.65 2.01 ppm) that is caused by the influence of deuteropyridine directly on the 6 -hydroxyl. Obviously one of the hydroxyls of the -D-glucopyranoside or -D-xylopyranoside residues has the same effect in this instance.     

On a variational method for determining excited state wave functions

A variational method is proposed which results in an approximate wave function for an excited state which has the maximum overlap with the true excited state eigenfunction. The method involves the calculation of the quantities E=¦H¦ and =¦(H-E)²¦, but is free of the constraint that the trial function must remain orthogonal to all states of the same symmetry which lie beneath it. One must know, however, an approximation to the true eigenvalue. A discussion is given on how one might gain the latter information, lacking knowledge of the spectrum, from the repeated application of the method.

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Zusammenfassung Es wird eine Variationsmethode vorgeschlagen, die auf eins genäherte Wellenfunktion für einen angeregten Zustand führt, welche sich maximal mit der wahren Eigenfunktion des angeregten Zustandes überlappt. Die Methode ermöglicht die Berechnung der Größen: E=¦H¦ und =¦(H-E)²¦, ist aber frei von der Nebenbedingung, daß die Versuchsfunktion orthogonal zu allen benachbarten Zuständen mit derselben Symmetrie bleiben muß. — Man will jedoch eine Näherung des wahren Eigenwertes wissen. — Eine Diskussion darüber, wie man durch wiederholte Anwendung der Methode letztere Information gewinnen kann, ohne Kenntnisse über das Spektrum zu besitzen, wird durchgeführt.

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Résumé Méthode variationnelle pour la détermination d'une fonction d'onde d'un état excité présentant le recouvrement maximum avec la fonction d'onde exacte. La méthode implique le calcul de E=¦H¦ et =¦(H-E)²¦ mais ne comporte pas la contrainte d'orthogonalité de la fonction d'essai à tous les états inférieurs de même symétrie. On doit cependant connaître une valeur approchée de la valeur propre exacte. Discussion sur la manière dont on peut obtenir cette valeur approchée sans connaître le spectre, par application répétée de la méthode.

     

Differential thermal analysis studies on the crystallization of strontium tungstate from sodium tungstate melt. Nucleation mechanism and induction periods

The nucleation mechanism, kinetics and induction periods in strontium tungstate crystallization from sodium tungstate melt in platinum crucibles were investigated by differential thermal analysis. Heterogeneous nuclei first formed on the metal platinate particles within the solution during the induction periods (¯t); the main crystal growth started only after ¯t and few new nuclei were then formed. At any crystallization temperature, ¯t varied inversely with the cooling rate (R _T), and with the rate (R_C) of development of excess solute concentration according to the relation ¯t = 1/(k ₁ R _c ), wherek ₁ and are constants. The critical temperature (¯T), critical supersaturation(¯ S), k ₁ and were evaluated.

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Zusammenfassung Der Keimbildungsmechanismus, sowie die Kinetik und die Induktionsperioden wurden bei der Kristallisation von Strontiumwolframat aus Natriumwolframatschmelzen in Platintiegeln durch Differentialthermoanalyse untersucht. Die heterogenen Kristallkeime wurden zuerst während der Induktionsperiode () an den Metallplatinat-Teilchen in der Lösung gebildet: das Hauptkristallwachstum begann erst nach und nachfolgend wurden einige neue Keime gebildet. Bei jeder Kristallisationstemperatur änderte sich umgekehrt proportional zu den Abkühlungsgeschwindigkeiten (R _T) und den Geschwindigkeiten (R _c) der Bildung überschüssig gelösten Materials, entsprechend der Gleichung = 1/(k ₁ R _c , wobeik ₁ und Konstanten sind. Die kritische Temperatur (¯T), die kritische Übersättigung (¯S),k ₁ und wurden bewertet.

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Résumé On a étudié par analyse thermique différentielle le mécanisme de nucléation ainsi que la cinétique et les périodes d'induction de la cristallisation du tungstate de strontium, à partir des bains fondus de tungstate de sodium, dans des creusets de platine. Des noyaux hétérogènes se forment d'abord sur les particules de platinate métallique dans la solution, au cours des périodes d'induction (): la croissance principale des cristaux ne commence qu'après et il se forme alors quelques noyaux nouveaux. A une température quelconque de cristallisation, varie de façon inverse avec les vitesses de refroidissement (R _T) et les vitesses de développement (R _c ) de concentrations de sursaturation de la substance en solution, selon la relation = 1/(k ₁ R _c , oùk ₁ et sont des constantes. On a évalué la température critique (¯T), la sursaturation critiques (¯S),k ₁ et.

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, . - (¯ t). ¯t . - ,¯t (R _T), (R _c) ¯t=1/(K₁ R _c ), ₁ — . (¯), (_-S), K₁ .

     

The thermal behaviour of solvates in the LiCI(MgCl2, AlCl3) water-1,4-dioxane systems

The thermal behaviour of the solvates and mixed solvates in the LiCl(MgCl₂, AlCl₃)-water-1,4-dioxane systems was investigated by means of DTA measurements of the melting behaviour and by quasi-isothermal and quasi-isobaric investigations of the thermal decomposition processes.The compounds melt incongruently. The positions of the melting points and the processes of thermal decomposition confirm the assumption that 1,4-dioxane is bonded in the first coordination sphere in the mixed solvate of lithium, but in the cases of magnesium and aluminium chloride it is bonded via hydrogen-bonds and not directly to the cations. Only for the lithium and magnesium compounds does the decomposition of the anhydrous solvates result in anhydrous chlorides.

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Zusammenfassung Das thermische Verhalten der Solvate und Mischsolvate der Systeme LiCl, (MgCl₂, AlCl₃)-Wasser-1,4 Dioxan wurde mit Hilfe von DTA-Messungen zum Schmelzverhalten, und quasi-isothermen und quasi-isobaren Untersuchungen zum Ablauf der thermischen Zersetzung Untersucht. Die Verbindungen schmelzen inkongruent. Die Lage der Schmelzpunkte und der Verlauf der thermischen Zersetzung bekräftigen die Vorstellungen, daß 1,4 Dioxan im Mischsolvat des Lithiums in der ersten Koordinationsphäre direkt am Kation, hingegen bei Magnesium und Aluminium über Wasserstoffbrücken gebunden ist. Die Zersetzung der wasserfreien Solvate führt nur im Fall der Lithium- und Magnesiumverbindungen zu den wasserfreien Chloriden.

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( , )--1,4- , - - — . . , 1,4- . , , . .

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The valuable assistance of Dr. Frahghänel in the separation of the solid phase by means of the hightemperature centrifuge is gratefully acknowledged.     

Investigation of surface phenomena on solid catalysts by simultaneous thermogravimetry and DTA

Thermogravimetry and simultaneous DTA were used to investigate the phenomena of adsorption, desorption and surface reactions on solid catalysts. The measurements were carried out with NaX and X-type ion-exchanged zeolites and silica-alumina gels (Ketjen) treated with sodium hydroxide in the presence of carbon dioxide. On the basis of the quantitative results it is possible to give an interpretation of the surface phenomena and to establish the existence of various active centres on the surfaces of the catalysts. In the case of the adsorption of carbon dioxide on X-type zeolites, the quantity of carbon dioxide adsorbed is much smaller on ion-exchanged zeolites than on NaX.

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Zusammenfassung Thermogravimetrie und simultane DTA wurden zur Untersuchung der Adsorptions-, Desorptions-Erscheinungen und Oberflächenreaktionen an festen Katalysatoren eingesetzt. Die Messungen wurden and NaX und Zeolithen des Typs X sowie an Silika-Aluminiumoxidgelen Ketjen durchgeführt, welche mit Natriumhydroxid in Gegenwart von Kohlendioxid behandelt worden waren. Aufgrund der quantitativen Ergebnisse ist es möglich eine Deutung der Oberfiächenerscheinungen zu geben und die Existenz verschiedener aktiver Zentren an der Katalysatorenoberfläche nachzuweisen. Im Falle der Adsorption von Kohlendioxid an Zeolithen des Typs X ist die Menge des adsorbierten Kohlendioxids am Ionenaustauscher viel niedriger als am NaX.

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Résumé Application de la TG et de l'ATD simultanées à l'étude des phénomènes d'adsorption, de désorption et de réactions de surface sur des catalyseurs solides. Les mesures ont été effectuées avec des zéolites échangeuses d'ions de type NaX et X ainsi qu'avec des gels Ketjen silice-alumine traités par NaOH en présence de CO₂. Les résultats quantitatifs permettent de donner une interprétation des phénomènes de surface et d'établir l'existence de divers centres actifs à la surface des catalyseurs. Dans le cas de l'adsorption de CO₂ sur les zéolites de type X, la quantité de CO₂ adsorbé est beaucoup plus faible que sur les zéolites de type NaX.

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DTA , . - NaX X - « », . . X, - , NaX.

     

Thermal and some other properties of the complexes crystallizing from the system Ni(II)-en-[Ni(CN)4]2−-H2O

Seven complex compounds exhibiting the compositions Ni(en)₃Ni(CN)₄·H₂O (I), Ni(en)₃Ni(CN)₄ (II),-Ni(en)₂Ni(CN)₄ (III), Ni(en)Ni(CN)₄·2H₂O (IV), Ni(en)Ni(CN)₄ (V), Ni(en)₂Ni(CN)₄ · 2.5H₂O (VI) and-Ni(en)₂Ni(CN)₄ (VII) were prepared from the system Ni-en-[Ni(CN)₄]^2–-H₂O. These compounds were examined by the methods of infrared spectroscopy, X-ray powder diffractometry, UV-VIS reflectance spectroscopy, and also by the measurement of magnetic moments. The thermal stability, the stoichiometry of thermal decomposition and the mutual transformations were investigated with a derivatograph. The reactions proceeding according to the following schemes were observed if the system was heated to appropriate temperature: (I)(II)(III)(V)(IV) and (VI)(VII)(III)(V)(IV) Process (VII)(III) represents isomerization. The reversibility of the process (V)(IV) is due to the high hygroscopicity of the anhydrous complex. The changes in structure in the course of the individual processes are discussed.

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Zusammenfassung Aus einem System Ni-en-[Ni(CN)₄]^2–-H₂O wurden sieben Komplexe der Formeln Ni(en)₃Ni(CN)₄·H₂O (I), Ni(en)₃Ni(CN)₄ (II),-Ni(en)₂Ni(CN)₄ (III), Ni(en)Ni(CN)₄·2H₂O (IV), Ni(en)Ni(CN)₄ (V), Ni(en)₂Ni(CN)₄ · 2.5H₂O (VI) und-Ni(en)₂Ni(CN)₄ (VII) hergestellt. Diese Verbindungen wurden mittels IR-Spektroskopie, Röntgenpulverdiffraktometrie, UV-Reflexionsspektroskopie und durch Messungen des magnetischen Momentes untersucht. Die Wärmestabilität, die Stöchiometrie des thermischen Zerfalles und die gegenseitigen Umwandlungen wurden mittels eines Derivatographen untersucht. Wird das System auf geeignete Temperaturen erhitzt, kann der Reaktionsverlauf durch folgendes Schema dargestellt werden: (I)(II)(III)(V)(IV) und (VI)(VII)(III)(V)(IV).Der Prozeß (VII)(III) verkörpert eine Isomerisierung. Die Umkehrbarkeit von Prozeß (V)(IV) ist auf die ausgeprägten Hygroskopieeigenschaften des wasserfreien Komplexes zurückzuführen. Es werden die im Ablaufe der einzelnen Prozesse vorgehenden Strukturveränderungen besprochen.

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Ni- -[No(N)]² -₂ Ni(en)₃Ni(CN)₄ · ₂ (I), Ni(en)₃Ni(CN)₄ (II),-Ni(en)₂Ni(CN)₄ (III), Ni(en)Ni(CN)₄-2H₂O (IV), Ni(en)Ni(CN)₄ (V), Ni(en)₂Ni(CN)₄ · 2,5H₂O (VI) -Ni(en)₂Ni(CN)₄ (VII). , , - , . , . (I)(II)(III)(V)(IV) (VI)(VII)(III)(V)(IV). (VII)(III) . (V)(IV) . .

     

Coke deposition on naphtha reforming catalysts: II. Influence of the addition of a second metal to platinum

The nature and rate of coke deposited on mono-and bimetallic reforming catalysts have been studied for normal heptane reforming. For bimetallic catalysts it has been shown that coke deposition is less extensive than on monometallic catalyst, depending on the degree of polymerization and the type of bimetallic catalyst.

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-. , , , .

     

On the problem of predicting the activity of oxide and carbonate catalysts in some reactions of petrochemical synthesis

The problem of predicting the activity of oxide and carbonate catalysts for some reactions of petrochemical synthesis (vapor phase conversion of carboxylic acids, catalytic oxidation of asphaltic tar to bitumen) according to the established dependence of thermal stability variations of intermediates on the formation enthalpy of metal oxides or standard ele.trode potentials is discussed.

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, ( , ) .

     

Interaction of nitric oxide with NiCr2O4

Interaction of NO with NiCr₂O₄ has been studied at 473–1173 K. It has been established that on nickel-chromium spinels NO decomposition practically does not take place. Nitric oxide can interact only with prereduced samples to reoxidize them.

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473–1173 NO NiCr₂O₄. , NO . (II) ; .

     

An Alternative Method of Introducing Fugacity

In current textbooks fugacity is introduced according to its differential or integral mathematical formulation. In this article an alternative method of explanation is offered. It is suggested that the real state of a pure gas can be described by comparing it to a hypothetical idealized state. The differences between these two states can then be expressed in terms of a function, , defined as (T,P) = _real(T,P) - _ideal(T,P) where _real and _ideal are the chemical potentials of the gas in its real and ideal states, respectively. The function is a molar excess quantity and is expressed as (T,P) = RT1n where is the fugacity coefficient. This approach introduces fugacity deductively through the function, which leads to , the fugacity coefficient. This method is also appropriate for introducing the activity of solution components and the fugacity of a real gas in gaseous mixtures.     

Nitrosation of mefenorex in the presence of cyclodextrins

- and -Cyclodextrin (CD) and heptakis-2,6-di-O-methyl--cyclodextrin (DIMEB) form soluble inclusion compounds with mefenorex (MEF); with -CD a partial inclusion occurs. No solid inclusion compound could be obtained with the four CDs. -, -CD and DIMEB, but not -CD, enhance the nitrosation rate of MEF if the nitrosation assay procedure (NAP test) is applied. During this reaction with - and -CD, solid inclusion compounds of the CDs and nitrosomefenorex (NMEF) precipitate.Part of the Ph.D. thesis of V. Wedelich, Freie Universität Berlin, 1985.     

Vibrational isotope effect by the low rank perturbation method

Mathematical formalism of the low rank perturbation method (LRP) is applied to the vibrational isotope effect in the harmonic approximation. A pair of two n-atom isotopic molecules A and B which are identical except for isotopic substitutions at atomic sites is considered. Relations which express vibrational frequencies _k and normal modes _k of the perturbed isotopic molecule B in terms of the vibrational frequencies _i and normal modes _i of the unperturbed molecule A are derived. In these relations complete specification of the unperturbed normal modes _i is not required. Only amplitudes | _i of normal modes _i at sites affected by the isotopic substitution are needed.