Theoretical am1 studies of inclusion complexes of α- and β-cyclodextrins with methylated benzoic acids and phenol,and γ-cyclodextrin with buckminsterfullerene

Semiempirical AM1 calculations have been performed on the inclusion complexes of - and -cyclodextrin with benzoic acid and phenol and -cyclodextrin with methylated benzoic acids in the head first and tail first positions. The results show that -cyclodextrin complexes with phenol and benzoic acid guests in the head first position are more stable than in the tail first position, while -cyclodextrin complexes with the same guests prefer the tail first position. The preferred orientation for -cyclodextrin with methylated benzoic acids is determined by the position of the methyl substituent(s). In general, para-methyl benzoic acid derivatives prefer the tail first position. -cyclodextrin forms a slightly unstable 1:1 complex with C₆₀ (3.4 kcal/mol), but two -cyclodextrins provide enough stabilization by about 10 kcal/mol to cage-in the C₆₀.     

Identification of the plant source of the Chinese crude drug „Dan-zhu-ye“ using the low-temperature plasma ashing technique

Summary A microchemical approach for the identification of plant source of Chinese diuretic crude drug Dan-zhu-ye using low-temperature plasma ashing is reported. The specimen was ashed on a microscope slide and the remaining ashed tissue was microscopically compared with other specimens of bamboo and bamboo grasses. Characteristic distribution patterns of silicon bodies and their shape in Dan-zhu-ye have suggested that the plant source of the crude drug isLophatherum sinense Rendle or at least its very close relative.

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Zusammenfassung Über die Ergebnisse der Tieftemperatur-Veraschung der chinesischen Rohdroge Dan-zhu-ye zwecks pflanzlicher Zuordnung dieses Diureticums wurde berichtet. Das Untersuchungsobjekt wurde auf einem Objektträger verascht und der Geweberückstand unter dem Mikroskop mit anderen Proben von Bambus und Bambusgräsern verglichen. Charakteristische Verteilungsmuster von Siliziumkörperchen und deren Form in Dan-zhu-ye legen die Annahme nahe, daß die Droge von Lophatherum sinense Rendle stammt oder ihm wenigstens sehr nahe steht.

     

Synthesis of micron-sized, monodisperse polymer particles of disc-like and polyhedral shapes by seeded dispersion polymerization

Micron-sized, monodisperse polymer particles having unique disc-like and polyhedral shapes were produced by seeded dispersion polymerization of various methacrylates with 1.57 m-sized polystyrene seed particles in the presence of saturated hydrocarbon droplets in methanol/water. Such nonspherical shapes were controllable by the polymerization conditions.Part CCLX of the series Studies on Suspension and Emulsion     

Determination of polychlorobiphenyls and polycyclic aromatic hydrocarbons in the atmospheric aerosol of the Venice Lagoon

An analytical method for simultaneous determination of particle-associated and gaseous-phase concentrations of polychlorinated biphenyls (PCB) and polycyclic aromatic hydrocarbons (PAH) in atmospheric aerosol samples obtained by high-volume samplers using polyurethane foam adsorbent (PUF) and quartz fibber filters (QFF) has been investigated. Quality control of the analytical procedure was carried out by blank control and by evaluating limits of detection, recoveries, accuracy, and repeatability. The proposed method was subsequently used to determine PAH and PCB in the gaseous and particulate phases of the aerosols that enter the Venice Lagoon atmosphere. The highest concentrations of PCB and PAH were predominantly in the gaseous phase. In both particulate and gaseous phases the penta-CB congeners dominated total PCB concentrations whereas phenanthrene, fluoranthene, and pyrene dominated the PAH concentrations. Total (gaseous plus particulate) PCB and PAH concentrations were higher at the site directly influenced by the industrial plants but the concentrations in marine aerosol samples were lower by a factor four only and must be taken into consideration when studying the chemical contamination of the Venice Lagoon.     

Natural flavours of wine: correlation between instrumental analysis and sensory perception

Summary The aroma of wine consists of 600 to 800 aroma compounds from which especially those, typical for the variety, are already present in the grapes. The aroma extracts — received by extraction with trichlorofluoromethane — are separated by gas chromatography. There are significant varietal differences between the aromagrams (fingerprint pattern). Thus the amount of some flavour compounds (key substances) shows typical dependence on the variety. Especially monoterpene compounds play an important role in the differentiation of wine varieties.The German white wines can be differentiated into three groups only by quantitative determination of 12 monoterpenes (terpene profile). These groups are: Riesling type, Muscat type and Silvaner-Weißburgunder type. Such terpene profiles are also useful for the separation of real Riesling wines from others called Riesling (e.g. Welschriesling, Kap Riesling, Emerald Riesling) but not produced from grapes of the variety Riesling. Including further components and by means of statistical methods as for example linear discriminant analysis even the different varieties within the mentioned groups (for instance the Riesling-group: Riesling, Kerner, Ehrenfelser, Bacchus, Müller-Thurgau) can be separated from each other.To identify compounds causing off-flavours the sniffing technique is the method of choice. The off-flavour is pinpointed during gas chromatography separation of the complex aroma mixture by effluent sniffing. Once allocated, the chemical nature of the off-flavours is elucidated by spectroscopic methods. Substances contributing to the green pepper taint, the strawberry note, mousiness, corkiness etc. in wine could be found in this way.     

Reaction of 3,4-dichlorocaranes with nucleophilic reagents

Conclusions 3,4-Dichlorocarane when subjected to acetolysis undergoes rearrangements that are characteristic for the carane system: ⁴-carene-p-1, 5-menthadiene, caraneethylbicyclohexane, and caranemethyl-isopropenylbicyclohexane.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 388–393, February, 1972.     

Preliminary phantom measurements for in vivo activation analysis of calcium in the human forearm

Preliminary phantom measurements were carried out for regional determination of calcium in the human forearm. Two paraffine phantoms /large and small/ were activated, either in the free space or surrounded by paraffine plates, by a²⁵²Cf neutron source. Differences between neutron flux densities in positions of the ulna and radius are discussed.     

Preparation of La(OH)3 colloids and tactoid structures

Summary Lanthanum(III) hydroxide colloids have been prepared by in situ and repeptization method. The in situ colloids were aggregated in schiller layers. The formation of the sol is a relatively slow process which accounts for a good uniformity of the particles size. The characteristic lateral array of the colloidal particles in Schiller layers could be destroyed by simple shaking the sample. Lanthanum(III)hydroxide sols prepared by the repeptization method were needle-shaped and not tactoidally orientated.

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Zusammenfassung Lanthan(III)hydroxid-Kolloide wurden in situ und durch Repeptisation hergestellt. Eine regelmäßige Aggregation der Kolloidteilchen wurde nur bei in situ bereiteten Solen beobachtet (SchillerSchichten). Die Bildung der Sole ist ein verhältnismäßig langsamer Prozeß, was mit der ziemlich engen Verteilung der Teilchengr6ßen zusammenhängen k6nnte. Die Schiller-Schichten werden durch Schütteln zerstört. Ein durch Repeptisation gebildetes Lanthan (III)hydroxid war nadelförmig ausgebildet und nicht taktoidal aggregiert.

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With 5 figures

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*) Our thanks are due to Dr. N. LjubeN for the electron microscopy work.     

Über das pseudoternäre System “ZrO”−ZrN−ZrC

The pseudoternary system ZrO–ZrN–ZrC and the corresponding pseudobinary systems ZrO–ZrN, ZrO–ZrC and ZrC–ZrN have been investigated by X-ray and metallographic techniques at 1600 and 2000°C.There is a considerable solid solubility of ZrO, which as a pure phase is not existent, in ZrC, ZrN and Zr(C, N). At 1600°C the boundary solubility of ZrO decreases from ZrC_0.45O_0.55 to ZrN_0,65O_0.35. The solubility of the oxide increases with the temperature to ZrC_0.25O_0.75 and ZrN_0.45O_0.55 at 2000°C.

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Mit 6 Abbildungen

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Herrn Prof. Dr.Otto Hromatka zum 70. Geburtstag gewidmet.     

Fractals and Percolation in the Theory of Porous Electrodes

A computer-aided simulation of the structure of a porous electrode is performed using flat lattices of sites (they are capable of conducting electrons and are randomly distributed in the electrode) as an example. To adequately describe properties of a porous electrode, information about the degree of dispersion of the particles that make up the electrode (fractal dimensionality) must be complemented by that on their clusterization (presence of percolation clusters). These factors impart two properties to a porous electrode, specifically, a developed surface, on which an electrochemical process may proceed, and the possibility of a continuous supply of electrons to this surface. A percolation cluster may be dismembered to a trunk (it provides for the electron transport) and a crown (aggregate of particles that make a major contribution to the electrochemical process). The dismembering was performed via computer flow diagrams proposed by the authors. A computer-aided analysis of characteristics of a porous electrode points to the existence of an optimum structure in which the electrochemical activity is capable of reaching a maximum.     

Measurement by ultra low level liquid scintillation counting following the Chernobyl accident

The situation in Austria following the Chernobyl accident is described shortly as well as applications of measurements with the ultra low level liquid scintillation counter Quantulus concerning milk, precipitation, surface water and drinking water. Data on the measurement of tritium are presented.     

The time evolution of the pair distribution function of polymeric systems

Summary The stress tensor of a polymeric system, solution or melt, is the sum of single molecule terms which may be expressed as integrals involving the distribution function in the phase space of a single molecule and intermolecular terms which involve the distribution function in the configuration space of pairs of molecules. The evaluation of the single molecule terms is usually based on the solution of the diffusion equation in the configuration space of a single molecule. In the present development, an analogous diffusion equation in the configuration space of a pair of molecules is developed. The development is based on a generalization of the time-smoothing ideas introduced by Kirkwood. Expressions are obtained for the various friction coefficients as time correlation functions.     

The structures of macrocyclic heterocyclophane inclusion complexes

Crystal and molecular structures of (1:1) molecular complexes of N,N,N,N-tetramethyl-2, 11, 20, 29-tetraaza [3.3.3.3] paracyclophane (1) with CHCl₃, CH₂Cl₂, CH₃CN and CO₂ are reported. The macrocycle has square-box structure, giving hydrophobic cavity surrounded by four benzene rings. The guest molecules are included in the cavity. The uncomplexed1 was found to have a rectangular form, indicating large conformational flexibility of1. In solution,1 is achiral because rapid RS interconversion, but in solid, the macrocyclic conformation is frozen as R-conformer or S-conformer. The macrocycles with the same chirality are stacked alongb-axis to form chiral molecular columns, R-colums or S-columns. Complexes of1 crystallize differently depending on the guest molecules. R-columns (S-columns) packed alonga-axis produce R-layers (S-layers), which are further packed alongc-axis using R-layer to R-layer contact (RR) or SS and RS or SR. The crystals of1·CHCl₃ are formulated as--RRR--=[R]_n (Type I, chiral) and those of1·CH₃CN or1·CO₂ and1·CH₂Cl₂ are represented by [RS]_n (Type IIA, racemic) and [RRSS]_n (Type IIB, racemic), respectively.     

Water-tree growth in low density polyethylene

In contrast to the degradation of polyolefinic insulations stressed by pure electrical, inhomogeneous fields of sufficient intensity (electrical treeing) the growth of water-trees (which require the presence of water in addition to the electrical load) has been found in some cases to be dependent on the morphology and the state of the resin. This state may be influenced by annealing.Water-treeing is accompanied by local accumulation of water requiring an enlargement of free volumes within the amorphous regions of the semicrystalline polymer. p]The results of our investigations may be interpreted by assuming annealing dependent variations of free volume size-distribution as well as annealing dependent resistance against deformations within the interior of the polymer which allow the growth of waterclusters.     

Structural Transformations in Polydisperse Ferrofluids

Real polydisperse ferrofluid is modeled by a bidispersed magnetic colloid composed of large and small particles. It is assumed that the energy of magnetodipole interaction for small particles is much lower and that of large particles is substantially higher than their thermal energy. Therefore, large particles can combine into the chain and droplet aggregates that are present in a sea of small particles. The influence of small particles on the structurization in the ensemble of large particles is studied. It is shown that small particles can either prevent or stimulate these structural transformations depending on the parameters of a medium.     

Zur gas-chromatographischen Analyse strahlenchemischer Reaktionsprodukte

Zusammenfassung Strahlenschemische Reaktionsprodukte sind für die gaschromatographische Analyse als komplizierte Mischungen zu betrachten. Große Flüchtigkeits- und oft extreme Konzentrationsunterschiede zwischen den Komponenten erschweren die Analyse und erfordern die Anwendung spezieller Methoden und Techniken der Probenvorbereitung und-aufgabe sowie der Trennung und Bestimmung nur der wirklich interessanten Komponenten. Doppelsäulentechniken unter Einbeziehung von heartcutting, backflushing und trapping in geschlossenen, automatisch steuerbaren Apparaturen spielen dabei eine wichtige Rolle.

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Gas chromatographic analysis of reaction products from chemical irradiation

Summary The products of chemical irradiation can be regarded, from the gas chromatographic point of view, as being complex mixtures whose analyses are made difficult by the large differences in volatility and concentration of the various components. Special techniques must be used in the sample preparation and introduction as well as in the exclusive separation and determination of the components of particular interest. An important rôle in this process is played by double column techniques with heartcutting, backflushing and trapping in an automatically controlled closed system.

     

Determination of molecular properties by the method of moments

Some precautions needed in the choice of weight functions when calculating wave functions by the method of moments are analysed. It appears that an important criterion for good weight functions is that the difference between the total and the truncated overlaps (both defined in the paper) be high.The method of moments is applied to wave functions involving Hylleraas-type correlation factors using weight functions made up of products of single-particle orbitals. The aim of the calculations is partly to test the criteria for good weight functions, partly a preparation of more extended calculations of a similar type.The new name of the institute is: Computer Application Research and Development Center of the Chemical Industries.     

Beiträge zur Chemie der Pyrrolpigmente, 72. Mitt.

A strategy for the synthesis of bilatrienes-abc bridged between rings A and C has been developed and tested in case of a bibenzylethane bridging fragment. This strategy was then applied to the synthesis of a 2,3-dihydrobilatriene-abc bridged by a (S)-lysine moiety from ring A to ring C (positions 3 and 12) by means of peptide bonds between the two amino groups of lysine and the acetic and propionic acid side chains of the chromophoric unit. The two diastereomers resulting from the two chiral centers of the lysine residue and at position 3 of the chromophore were separated by chromatography.

     

Analytical Chemistry — today''s definition and interpretation

Conclusion Although this multidisciplinary branch of science is growing rapidly today, yet two main points remain unchanged. On the one hand, it is analytical in essence; on the other, the information which it aims to acquire is chemical in nature, i.e. within the domain of chemistry. Accordingly it seems pertinent to reserve the term Analytical Chemistry for it. Other terms like analytical physics and chemical characterization are one-sided, with the aim or essence missing. The same is true of analytics and analytical science. Moreover, they should, literally speaking, include analytic geometry, analytical mechanics and so on.     

Chemical shifts of aqueous nonelectrolyte solutions: Influence of the polar and nonpolar groups on the water proton shifts at 0°C

Hydroxyl-proton chemical shifts of alcohol mixtures and aqueous solutions containing some nonelectrolytes (alcohols, ketones, cyclic ethers, and amines) have been measured at 60 MHz and at 0°C. Methyl-proton resonance of the solutes was used as the internal reference and the water-proton shifts in solutions were measured with respect to pure water. Downfield shifts for some alcohols (particularly tertiary butanol and iso-propanol), cyclic ethers, and amines in the water-rich region were confirmed For alcohols and some other nonelectrolytes in water, the observed shifts were decomposed to component contributions arising from the polar group effect, solute proton effect, and nonpolar group effect. Polar effects are found to contribute a substantial fraction of the observed downfield shifts. After subtracting these polar contributions, however, there still remains certain amounts of downfield shifts which may be attributed to the effect of nonpolar groups on the water structure. The downfield shifts are found to be relatively large when the solutes have branched alkyl groups with nearly spherical shape and with diameters of about 5 Å. Strikingly large downfield shifts of water proton resonance were found for some secondary amines and tertiary diamines with globular shape. However, in view of the extrapolation technique employed in evaluating the polar group effect, the downfield nonpolar group effect we estimated should be considered as the upper limits.Work done at Professor Hertz's laboratory in Karlsruhe on a sabbatical leave from Clark University.