An Efficient, One-Pot, Triton-B Catalyzed Synthesis of O-Alkyl-S-methyl Dithiocarbonates

Summary. A novel process for the one-step conversion of a variety of primary and secondary alcohols into their O-alkyl-S-methyl dithiocarbonates using methyl iodide catalyzed by the Triton-B/CS₂ system was developed. Thus, O-alkyl-S-methyl dithiocarbonates were obtained in very good to excellent yields. This protocol is mild and efficient compared to other methods.     

Triton-B Catalyzed, Efficient, One-Pot Synthesis of Carbamate Esters from Alcoholic Tosylates

Summary. A novel process for the one-step chemoselective conversion of a variety of alcoholic tosylates into carbamates serving as protected amines was developed using benzyltrimethylammonium hydroxide (Triton-B) in the presence of gaseous carbon dioxide. Thus carbamate esters of different amines were prepared in very good to excellent yields. Present address: Institute of Organic and Biomolecular Chemistry, Georg-August University, D-37077, G?ttingen, Germany     

Die katalytische Protonenstufe des Diisopropylamino-äthanthiol-Hydrochlorids in Gegenwart von Kobalt(II)

Diisopropylaminoethanethiol hydrochloride (DIAPAET · HCl) in ammoniacal cobaltous chloride solution gives rise to a catalytic hydrogen wave. The effects of various factors such as concentration ofDIPAET · HCl, concentration of Co(II), buffer capacity, pH, salts, surface active substances and height of Hg-column on the characteristics of the wave have been studied.

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Mit 3 Abbildungen     

Versatile Use of Carbon Dioxide in the Synthesis of Carbamates

Summary. Organic carbamates classically have been synthesized using harmful and toxic reagents like phosgene, its derivatives, and carbon monoxide. Recently, carbon dioxide was used as a cheap and harmless reagent for the synthesis of organic carbamates in the gaseous or supercritical state, or in an electrochemical process, or organic carbonates as sources of carbon dioxide as an alternative to the harmful reagents. The present review will deal with the extensive use of carbon dioxide in the synthesis of organic carbamates.     

Conductivity of a lattice-gas with Coulomb-interactions

A theory for the conductivity of a three-dimensional regular lattice-gas of charged particles is formulated. The hopping-motion of the particles is described by a masterequation. From the density-response-function at long wave-lengths the dynamic conductivity () is derived. Its high-frequency limit () and the corresponding activation energy are calculated by using the mean-spherical approximation for the corresponding static correlation functions. For systems with weak or intermediate coupling the dynamic part of the conductivity is computed within mode-coupling theory. The results are compared with hopping models based on short-range interactions.     

High spin spectroscopy of 139Pr

The high spin states in N=80 ¹³⁹Pr have been investigated by in-beam γ-spectroscopic techniques following the reaction ¹³⁰Te (¹⁴N, 5n) reaction at E=75 MeV, using a gamma detector array, consisting of seven 23% compton-suppressed high purity germanium detectors and a multiplicity ball of fourteen bismuth germanate elements. Based on γ-γ coincidence data, the level scheme of ¹³⁹Pr has been considerably extended up to 7.2 MeV excitation. Tentative spin-parity assignments are done for the newly proposed levels on the basis of the DCO ratios corresponding to strong gates and the available information from the earlier light ion experiments.     

Stochastic diagrams for critical point spectra

A new technique for calculating the time-evolution, correlations and steady state spectra for nonlinear stochastic differential equations is presented. To illustrate the method, we consider examples involving cubic nonlinearities in an N-dimensional phase-space. These serve as a useful paradigm for describing critical point phase transitions in numerous equilibrium and non-equilibrium systems, ranging from chemistry, physics and biology, to engineering, sociology and economics. The technique consists in developing the stochastic variable as a power series in time, and using this to compute the short time expansion for the correlation functions. This is then extrapolated to large times, and Fourier transformed to obtain the spectrum. Stochastic diagrams are developed to facilitate computation of the coefficients of the relevant power series expansion. Two different types of long-time extrapolation technique, involving either simple exponentials or logarithmic rational approximations, are evaluated for third-order diagrams. The analytical results thus obtained are compared with numerical simulations, together with exact results available in special cases. The agreement is found to be excellent up to and including the neighborhood of the critical point. Exponential extrapolation works especially well even above the critical point at large N values, where the dynamics is one of phase-diffusion in the presence of a spontaneously broken symmetry. This method also enables the calculation of the steady state spectra of polynomial functions of the stochastic variables. In these cases, the final correlations can be non-bistable even above threshold. Here logarithmic rational extrapolation has the greater accuracy of the two extrapolation methods. Stochastic diagrams are also applicable to more general problems involving spatial variation, in addition to temporal variation. Received: 12 January 1998     

Trisulfide‐Bond Acenes for Organic Batteries

The molecular design of organic battery electrodes is a big challenge. Here, we synthesize two metal‐free organosulfur acenes and shed insight into battery properties using first‐principles calculations. A new zone‐melting chemical‐vapor‐transport (ZM‐CVT) apparatus was fabricated to provide a simple, solvent‐free, and continuous synthetic protocol, and produce single crystals of tetrathiotetracene (TTT) and hexathiapentacene (HTP) at a large scale. Single crystals of HTP showed better Li‐ion battery performance and higher cycling stability than those of TTT. A two‐step, three‐electron lithiation mechanism instead of the commonly depicted two‐electron mechanism is proposed for the HTP Li‐ion battery. The superior performance of HTP is linked to unique trisulfide bonding scenarios, which are also responsible for the formation of empty channels along the stacking direction. In‐depth theoretical analysis suggests that organosulfur acenes are potential prototypes for organic battery materials with tunable properties, and that the tuning of sulfur bonds is critical in designing these new materials.     

Nuclear reaction analysis: A study on the interface formation in polymer mixtures below the critical point

We describe a method for directly determining the composition profile of deuterated polymer chains in polymer mixtures. Our technique, nuclear reaction analysis, is based on the ²H(³He, ⁴He)¹H nuclear reaction. By detecting ⁴He in a forward geometry, we achieve a spatial resolution of 14 nm (FWHM). We use this technique to probe the broadening of the interface between two partially miscible polymers. We found that such a system attains a finite interfacial width in equilibrium. For short times, we monitor the dynamics of interface formation. We found that the interfacial width increases significantly slower than in the case of free diffusion.