Phasentransferkatalysatoren auf Basis von Saccharose-Ethylenoxid-Addukten

Sucrose ethyleneoxide adducts have been prepared by reaction of sucrose with various amounts of ethyleneoxide inDMSO. The resulting polypode molecules were found to be efficient phase transfer catalysts in nucleophilic substitutions, oxidation and dichlorcarbene generation. Polymerisable polypodes have been obtained by reaction of sucrose ethyleneoxide adducts with methacrylic anhydride or methacryloylchloride in pyridine. Free radical polymerisation of the resulting mixtures of mono- and polyfunctional methacrylic esters of sucrose ethyleneoxide adducts yielded crosslinked gels. These polymer-supported octopus-molecules were found to be efficient triphase catalysts.

     

Kalorimetrische Messungen an Mischungen von Nichtelektrolyten, 1. Mitt.: Molwärme des Systems 1,2-Dibromäthan-Benzol

Zusammenfassung Es wird der Aufbau eines Kalorimeters zur Bestimmung der spezif. Wärme von Flüssigkeiten beschrieben. Die Messungen werden nach einem kontinuierlichen adiabatischen Aufheizverfahren durchgeführt. Der Fehler in der Molwärme beträgt ca. ±0,4%. Die Methode erlaubt auch innerhalb relativ kleiner Temperaturbereiche eine Aussage über die Temperaturabhängigkeit der Wärmekapazität.Die Molwärme des Systems 1,2-Dibromäthan-Benzol wird zwischen 24 und 29°C über den ganzen Konzentrationsbereich vermessen. Die Mischungen zeigen negative C _p-Werte mit unsymmetrischem Konzentrationsverlauf. Für höhere Temperaturen ist eine Zunahme der Symmetrie zu erwarten.

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A calorimeter has been described which serves to determine the heat capacities of liquids. In the measurements the calorimeter and the surroundings are heated continuously, so that adiabatic conditions prevail. The experimental error in the molar heat capacities is ca. ±0,4%. The method also permits the estimation of the temperature dependence of the heat capacities, even within relatively small temperature intervals.The molar heat capacity of the system 1,2-dibromoethane-benzene has been measured between 24° and 29°C for all concentrations. The C _p-values of the mixtures are negative and show an asymmetrical dependence on the concentration. For higher temperatures it is expected that the concentration dependence will become more nearly symmetrical.

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Mit 3 Abbildungen     

Computer-Assisted Solution of Chemical Problems—The Historical Development and the Present State of the Art of a New Discipline of Chemistry

The topic of this article is the development and the present state of the art of computer chemistry, the computer-assisted solution of chemical problems. Initially the problems in computer chemistry were confined to structure elucidation on the basis of spectroscopic data, then programs for synthesis design based on libraries of reaction data for relatively narrow classes of target compounds were developed, and now computer programs for the solution of a great variety of chemical problems are available or are under development. Previously it was an achievement when any solution of a chemical problem could be generated by computer assistance. Today, the main task is the efficient, transparent, and non-arbitrary selection of meaningful results from the immense set of potential solutions—that also may contain innovative proposals. Chemistry has two aspects, constitutional chemistry and stereochemistry, which are interrelated, but still require different approaches. As a result, about twenty years ago, an algebraic model of the logical structure of chemistry was presented that consisted of two parts: the constitution-oriented algebra of be- and r-matrices, and the theory of the stereochemistry of the chemical identity group. New chemical definitions, concepts, and perspectives are characteristic of this logic-oriented model, as well as the direct mathematical representation of chemical processes. This model enables the implementation of formal reaction generators that can produce conceivable solutions to chemical problems—including unprecedented solutions—without detailed empirical chemical information. New formal selection procedures for computer-generated chemical information are also possible through the above model. It is expedient to combine these with interactive methods of selection. In this review, the Munich project is presented and discussed in detail. It encompasses the further development and implementation of the mathematical model of the logical structure of chemistry as well as the experimental verification of the computer-generated results. The article concludes with a review of new reactions, reagents, and reaction mechanisms that have been found with the PC-programs IGOR and RAIN.     

Novel diode laser-compatible fluorophores and their application to single molecule detection, protein labeling and fluorescence resonance energy transfer immunoassay

We describe a series of new long-wave absorbing and fluorescing cyanine dyes and labels (based on a general logic for the design of such dyes), their spectra, covalent and noncovalent linkage to proteins, their use in single molecule detection (SMD) and as donors and acceptors, respectively, in fluorescence resonance energy transfer studies. The new labels represent water-soluble and reactive fluorophores whose quantum yields increase substantially if noncovalently or covalently bound to proteins. Due to their strong absorptions between 550 and 700 nm they are excitable by light-emitting diodes or diode lasers. Their high absorbances (epsilon around 100,000) and adequate fluorescence quantum yields (phi up to 0.68 if bound to proteins) along with their availability as reactive NHS esters make them viable labels for proteins and oligomers, e.g. in context with SMD or fluorescence energy transfer immunoassay which is demonstrated for the system HSA/anti-HSA.     

A Helmholtz-Lie type characterization of ellipsoids,II

A closed convex surfaceS in is an ellipsoid if and only if for anyx, y εS there is an affinity mappingx ontoy and a neighborhood ofx inS onto a neighborhood ofy inS.     

Aktivierungsanalytische Untersuchungen an standardisierten Eisenlegierungen. I

Zusammenfassung In zwei standardisierten Legierungen, und zwar in NBS-1138 Cast Steel 1 und NBS-1140 Ductile Iron 1, wurde Vanadin mit Hilfe der Neutronenaktivierungsanalyse und der Gamma-Spektrometrie zerstörungsfrei bestimmt.Bei den Vorversuchen zur Optimierung der Meßbedingungen wurden außer den in den provisorischen Zertifikaten angegebenen Elementen in NBS-1138 zusätzlich noch Arsen und Antimon, in NBS-1140 Antimon und Lanthan qualitativ nachgewiesen.

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Activation analytical studies of standardized iron alloys. I

Summary Vanadium was determined without interference by means of neutronactivation analysis and gamma spectrometry in two standardized alloys, namely in NBS-1138 Cast Steel 1 and NBS-1140 Ductile Iron 1. In the preliminary trials for determining the optimation of the measurement conditions the presence of arsenic and antimony was established qualitatively in addition to the elements stated provisionally in the certificate describing NBS-1138, and likewise antimony and lanthanum were found in the NBS-1140.

     

On the equivalence of different order parameters and coexistence of phases for Ising ferromagnet. II

We investigate Ising spin systems with general ferromagnetic, translation invariant interactions,H=–J _BB,J _B0. We show that the critical temperatureT _i for the order parameterp _i defined as the temperature below whichp _i>0, is independent of the way in which the symmetry breaking interactions approach zero from above. Furthermore, all the equivalent correlation functions have the same critical exponents asT T_i from below, e.g. for pair interactions all the odd correlations have the same critical index as the spontaneous magnetization. The number of fluid and crystalline phases (periodic equilibrium states) coexisting at a temperatureT at which the energy is continuous is shown to be related to the number of symmetries of the interactions. This generalizes previous results for Ising spins with even (and non-vanishing nearest-neighbour) ferromagnetic interactions. We discuss some applications of these results to the triangular lattice with three body interactions and to the Ashkin-Teller model. Our results give the answer to the question raised by R.J. Baxter et al. concerning the equality of some critical exponents.Supported by NSF Grant PHY 77-22302     

Strukturviskosität von verdünnten Lösungen von Biopolymeren

The importance of the rheological behaviour of solutions of macromolecules is briefly evaluated. The viscosity of the solutions depends on concentration, shear rate and time of shear, this relation being determined by the structure of the dissolved molecules. In dilute solutions shear dependence of viscosity is very frequently caused by the preferential orientation of anisotropic molecules. In such a case the particle dimensions can be calculated from the true limiting viscosity number, an anisotropy factor, the rotational diffusion constant and the effective particle density. These numbers can be derived from the flow curve, which has been extrapolated to zero concentration. It is necessary to measure the flow curve at shear gradients, which are sufficiently low to allow for an extrapolation to vanishing shear rate. By comparing the experimental flow curve with a choice of theoretical ones, the rotational diffusion constant and the anisotropy factor (axial ratio) can be found. From the limiting viscosity number and the axial ratio, the particle density can be calculated.     

On the equation of state of classical one-component systems with long-range forces

Several definitions of the pressure are introduced for one-component systems and shown to be nonequivalent in the presence of a rigid neutralizing background. Relations between these pressures are derived for finite and infinite systems; these relations depend on the asymptotic behavior of the force at infinity, with the Coulomb force at the borderline between different properties. It is argued that only one of those definitions is physically acceptable and its properties are discussed in relation to the asymptotic behavior of the force. It is seen in particular that a knowledge of the state of the infinite system is not sufficient to determine its thermodynamic properties. The results are illustrated by some typical examples.For example, for two-dimensional systems with three-dimensional Coulomb interaction see refs. 2–4.