Study of Preparation and Properties of Imidazolium Betaines

To investigate the posibility for the preparation of 1,3-dicarboxyalkyl( benz)imidazolium betaines a number of monosubstituted 1-carboxyalkyl(benz)imidazoles has been prepared (I-X) and their basic pKa value determined. The betaines (XI~XIV) can be prepared only from the imidazole derivatives which had basic (N3) pKa values above 3--4 pKa units. !-Substituted benzimidazoles decomposed under reaction conditions employed ·for quaternization, yielding N,N\u27-dicarboxyalkyl o-phenylenediamines. Dimethylformamide when used as the solvent under highly basic reaction conditions reacted with halogen carboxylic acid.s giving · rise to the formation · of betaines of dimethyl-dicarboxyalkyl amines (XV, XVI) and hydrochlorides of dimethyl-carboxyalkyl amines (XVII, XVIII), respectively. The reaction course of 1,3-disubstitution is briefly discussed, as well as some chemical and physical properties of the betaines are described

Nonlocal microscopic theory of quantum friction between parallel metallic slabs

We present a new derivation of the friction force between two metallic slabs moving with constant relative parallel velocity, based on T=0 quantum-field theory formalism. By including a fully nonlocal description of dynamically screened electron fluctuations in the slab, and avoiding the usual matching-condition procedure, we generalize previous expressions for the friction force, to which our results reduce in the local limit. Analyzing the friction force calculated in the two local models and in the nonlocal theory, we show that for physically relevant velocities local theories using the plasmon and Drude models of dielectric response are inappropriate to describe friction, which is due to excitation of low-energy electron-hole pairs, which are properly included in nonlocal theory. We also show that inclusion of dissipation in the nonlocal electronic response has negligible influence on friction

Image-potential states on clean and hydrogen-covered Pd surfaces: Analysis of a one-dimensional model

Theoretical calculations in a one-dimensional model give the energies of surface states on clean and hydrogen-covered Pd surfaces in very good agreement with those measured by high-resolution electron energy-loss spectroscopy and inverse photoemission experiments. Some general properties and the applicability of this class of one-dimensional models are discussed

Chiral 1,4-Benzodiazepines. VIII. Concerning the Rate of WD Exchange and Optical Stability of the Chiral Centre C(3).

Various chiral substituted 1,4-benzodiazepin-2-ones with 3- -acyloxy (general formula I), 3-hydroxy- and 3-alkoxy (general formula II), 3-alkyl (general formula III) and 3-quaternary ammonium (general formula IV) groups as substituents were subjected to C(3)-H-D exchange rate measurements in order to obtain information on the optical stability of the chiral centre and on the mechandsm of racemization. Only type IV compounds (IVa-j) exhibited H/D exchange, but acid catalyzed racemization took place in type I and II compounds, indkating some other mechani. sms in this process. Type III compounds as free bases (IIIa-c), N4-protonated acids, or N4-oxides (III, e; f) underwent no H/D exchange and are optically sfable as well. In cases whe,re deprotonation- reprotonation mechanism of racemization can be excluded two other mechanisms are discussed, i. e. acid-\u27catalyzed ring-chain tautomerism and identity substitution with alkoxide ion

Syntheses of the New Indole Derivatives Related to Indomethacin

Syntheses and properties of the new indole derivatives 18-33, being potential antiinflammatoric agents, are described. 1-p-Chlorobenzoyl- 2-methyl-3-(2\u27-methyl-4\u27-nitroimidazol-1\u27-yl)-5-methoxyindole (32) have been found to possess pronounced antiinflammatoric activity and very low ulcerogenity. Attempting preparation of N-benzoylindole derivative 38 via sigmatropic rearrangement of the open chain precursor 35, as a model procedure for the new synthesis of indomethacin, very low yields on the desired cyclic product 38 have inevitably been obtained

N 1-Substitution in 2-Methyl-4(5)-Nitroimidazole. II.

During the syntheses of some new derivatives of 2-methyl-4(5)nitroimidazole with potential antitrichomonal activity, we have noticed that the substitution on N 1 did not always depend on the pH of the medium, as it has been stated by Pyman1- 4 and Grimison et al.5- 8 • Therefore, we have approached the syste matic investigations of the influence of pH on the formation of t h e 4-nitro and 5-nitroisomers of N1- s ubstituted 2-methyl-4(5)-nitroimidazole. The results obtained indicate that the conclusion of Pyman1- 4 is valid only when strongly alkylated agents are applied, e. g. dialkylsulphates and alkyl tosylates9, since, with other alkylated agents this conclusion could be applied only with restrictions· In addition, we have measured pK:i constants for some isomer pairs prepared, in order to apply the statem ent of Grimison et al.6 that the tautomer ratio, calculated from pKa values, determines the ratio of the isomers in the product mixture . In spite of the fact that the pKa measurements were in goo d accordance with some earlier perform e d6 ,10,15, N 1-substitution with a number of alkylating agents indicate that the statement of Grimison et al.5- 8 is of importance only for alkylation with dimethylsulphate under strictly d e termined conditions

Unoccupied surface states on Pd(111) observed in very-low-energy electron diffraction and inverse photoemission: Theoretical interpretation

A three-dimensional calculation of projected electronic bulk and surface bands, spanning the energies studied by inverse photoemission and very-low-energy electron diffraction, reveals that the surface-electronic states observed by the two techniques are indeed two distinct states. We discuss their true character and the question of effective masses, and briefly comment on the validity of one-dimensional models

Synthesen von em1gen pharmakologisch und stereochemisch interessanten Derivaten der Camphansaure

In der vorliegenden Arbeit wird die Herstellung von Camphansaurederivaten III-XIII beschrieben. Von den Verbindungen VVIII und XIII wurde eine tuberkulostatische Wirkung erwartet. In vitro Untersuchungen der Verbindungen V-VIII ergaben jedoch durchaus negative Resultate. Die Derivate XIV-XX wurden als potentiell brauchbare chirale Reagenzien zubereitet. Silbersalz XIV wurde erfolgreich filr die Trennung von 3-Hydroxyderivaten der 1,4-Benzodiazepin-2-onen durch die Ester XVII a, b verwendet, ebenso wie Camphansaure filr die Trennung von Enantiomeren des 2-Aminobutanol-1 durch ihre diastereomeren Salze (XXII a, b)