Peculiarities of the effect of the electronic nature of substituents on the basic properties of aliphatic amines

Changes in the hybrid state of atomic orbitals of nitrogen and p-character of LEP, which occur under the effect of saturated hydrocarbon radicals and polar substituents in aliphatic amines, differ substantially. Therefore, the effect of the both substituents on the basicity constants of amines cannot be described by the single formal type of interaction. The anomalous changes in the basicity in the series of primary, secondary, and tertiary alkylamines, which are discussed in the literature, and the correlations pK _BH+ = f(*) and G _B = f(*) are, in fact, imaginary, because the alkyl radicals at the N atom do not manifest the electron-donor properties.     

Hydrolysis of 1,2-disubstituted imidazolines in aqueous media

The kinetics of hydrolysis of 1,2-disubstituted imidazolines in aqueous media was studied (pH 2.0—12.5, T = 25—90 °C) by UV spectroscopy. The hydrolysis products were identified. The introduction of a branched substituent into position 2 of the imidazoline ring increases the hydrolytic stability of the compounds. The effect of the pH on the hydrolysis rate of imidazolines is discussed.     

Components of <Emphasis Type="Italic">Artemisia pontica</Emphasis>

Chemical components from the aerial part of the Kazakhstan population of Artemisia pontica, from which the rarely encountered flavonoids 7-O-methyl- and 4′,7-di-O-methyl-esters of apigenin were isolated for the first time, were identified. The complete chemical composition of the essential oil was established using GC-MS.__________Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 143–145, March–April, 2005.     

Proton magnetic relaxation study of water orientation around I− and Li+

Proton relaxation time measurements are performed for 6m aqueous solutions of⁷LiI and⁶LiI in D₂O containing small amounts of H₂O. The measurements are done at low temperatures and yield maxima of the relaxation rate plotted against 1/T. From the maxima of the relaxation rates, proteon-I^– and proton-Li⁺ distances in the first coordination sphere of the ions are determined, and from the knowledge of the ion-water oxygen distance it is shown that for iodide a somewhat broadened H-bonded configuration is valid and that for Li⁺ the electric dipole orientation deviates from the radial direction. In order to test the reliability of the method a proton-¹²⁷I interaction study is also performed in KI solution in glycerol. The I-H distance obtained is in satisfactory agreement with that found in the aqueous system.     

Emission,Emissionslebensdauer und Absorption von [Cr urea6]X3-Einkristallen

Emission and absorption polarization spectra as well as emission lifetimes between room temperature and 5 °K have been measured of [Cr urea₆]X₃ single crystals, where X stands for ClO ₄ ^– , J^–, NO ₃ ^– , Br^–, Cl^–, F^–, and X₃ for JSO ₄ ^3– . The strong temperature dependence of the fluorescence/phosphorescence-ratios, and of the emission lifetimes is discussed. The differences between the spectra as well as the emission lifetimes of the various salts can be attributed to an anion dependent trigonal perturbation.

Die Autoren danken dem Verband der Chemischen Industrie für finanzielle Unterstützung dieser Arbeit.     

Thermodynamic and spectroscopic properties of mixtures of β-lactoglobulin and dioleylphosphatidylcholine

 The behavior of the single spreading monolayers of β-lacto-globulin (β-LG) and dioleyl-phosphatidylcholine (DOPC), as well as their mixtures, has been studied on subphases containing Na⁺ or Ca⁺⁺ ions. The results show an influence of temperature and subphase on the studied systems. The behavior of the areas as a function of the weight fraction of the two components shows significative and prevalently positive deviations from the additivity and their bidimensional miscibility. The variation of ΔG ^ex, ΔH ^ex and ΔS ^ex calculated for the DOPC–β-LG mixture having maximum deviation on two different supports allows to deduce that the interactions are prevalently repulsive. FTIR–ATR spectra of transferred plurilayers show that DOPC has a surface orientation which can originate the miscibility between the protein and DOPC. Received: 3 February 1997 Accepted: 3 June 1997     

The effect of the solvents on the specific intramolecular C-H...N interactions studied by1H NMR spectroscopy

The analysis of the effect of the solvents on the proton chemical shifts in¹H NMR spectra of 2-vinyloxypyridine indicates that the C—H...N interaction of weak intramolecular hydrogen bond type hinders the formation of intermolecular hydrogen C—H...X and C-H... bonds. The protonating solvents reduce the intramolecular C—H...N interaction due to association with the N atom of the pyridine cycle.Translated fromIzvestiya Akademii Nauk. Seriya Khimieheskaya, No. S, pp. 1202–1204, May, 1996.     

Optimization of alkali-alkalkine earth cation separation on weak cation-exchangers

Summary The elution behavior of alkali and earth alkaline cations has been studied on a newly synthesized weak cationexchanger (WCX). Applying this stationary phase isocratic separation of these cations is possible. The dependence of retention on competing ion concentration is described via a simple model. The influence of crown ethers as well as organic eluent additives on selectivity and peak efficiency is demonstrated. With optimized separation such cations can be determined with detection limits of about 0.5 ppm using a conductivity detector without ion suppression.     

合成云母蒙脱石及其交联物在乙醇氨化反应中的催化行为

用水热法合成了云母蒙脱石,并与羟基铝齐聚物交联,DTA和IR结果表明,由于柱的引进,高温焙烧时层内八面体上羟基脱除变得较为容易。由NH_3-TPD和吡啶吸附测得的表面酸性表明Al-CLS具有较SMM更多的弱酸和强酸中心。催化剂上弱酸中心有利于醇的脱水,而吸附在强酸中心上的NH_3有利于醇的胺化。     

The computation of the representation matrices of the generators of the unitary group

A method is presented for the efficient computation of the representation matrices of the unitary group, U(n) in the Gelfand—Tsetlin basis (corresponding to the usual spin-symmetry adapted basis for an N electron CI). The present scheme is conceptually and computationally attractive in that it is formulated directly in terms of Weyl tableaux and also that it permits simultaneous basis vector generation and matrix element evaluation. In addition the basis vectors are ordered so that subsequent restriction to the three dimensional rotation group is facilitated. An illustrative example is also presented.Taken in part from a thesis submitted to the University of London in partial fulfilment of the requirements for the degree of PhD.