Amarantholidols and amarantholidosides: new nerolidol derivatives from the weed Amaranthus retroflexus

Seven new sesquiterpenes, with nerolidol skeleton, have been isolated and characterized from the plant Amaranthus retroflexus, one of the major weeds of the world. The structures have been elucidated on the basis of spectroscopic data. The compounds have been characterized by the presence of hydroxyl groups or a glucopyranosyl moiety in the molecules. The configurations have been determined using Mosher's method. The compounds have been tested for their phytotoxicity on the test species Lactuca sativa. The bioassays showed an inhibitory effect on seed germination for all of compounds at the lowest concentrations.     

Na2CrO4-NaF-NaI and K2CrO4-KF-KI three-component systems

Na₂CrO₄-NaF-NaI and K₂CrO₄-KF-KI three-component systems have been studied by differential thermal analysis (DTA). The compositions and melting temperatures have been determined and the enthalpies of melting have been measured for eutectic mixtures. Phase equilibria in the title systems have been described, and phase fields have been demarcated.     

Thermodynamic properties of DCl in D2O solution from 5 to 50°C

The themodynamic properties of solutions of deuterium chloride (DCl) in deuterium oxide (D₂O) have been determined from emf measurements of the electrochemical cell without transference from 5 to 50°C, and from 0.002 to 1.0 mol-kg^–1. The standard potential of the silver/silver chloride electrode relative to the platinum/deuterium electrode has been determined. An equation for the Gibbs energy as a function of temperature has been derived from which the enthalpy, entropy, and heat capacity have been computed. Equations for the activity coefficient and the osmotic coefficient of DCl in D₂O have been developed. The excess Gibbs energy of the solution and the excess partial molar free energy as a function of temperature have been calculated, from which the other excess thermodynamic properties have been computed. The values for the heat capacity and the apparent molar heat capacity have been compared with calorimetric data in the literature. The relative partial molar enthalpy has been calculated. The solvent isotope effect on the excess thermodynamic functions is discussed.     

Solution properties of poly(N-vinyl carbazole)—II. Thermodynamic properties in various solvents

Thermodynamic properties of dilute solutions of Poly-N-vinyl carbazole obtained by cationic polimerization have been studied by viscometry in various solvents. The validities of some excluded volume theories have been tested and the unperturbed dimensions have been calculated. The dependence of molecular dimensions, 〈s²〉, on molecular weight and viscometric equations have also been determined.     

Alkaloids ofNitraria sibirica. Structure and absolute configuration of sibirinine

The chemical properties of sibirinine have been studied, its synthesis has been performed, and its¹H and¹³C NMR spectra have been analyzed. From the results obtained its structure and absolute configuration have been deduced.     

Solution properties of poly(N-vinyl carbazole)—III: Excluded volume theories and theta temperature

Thermodynamic properties of dilute solutions of poly-N-vinylcarbazole have been studied by viscometry in chlorobenzene and nitrobenzene at several temperatures. The validities of some excluded volume theories have been tested and the unperturbed dimensions have been calculated; for two of these theories in particular, no dependence of unperturbed dimensions on temperature and solvent has been found. The viscometric equations have also been determined. The theta temperatures for PNVC in chlorobenzene and nitrobenzene are ? 36.5 and ? 20.4°C respectively.     

Unimolecular rearrangements of ethylnitrene: An exploratory theoretical study

The products of the rearrangement of ethylnitrene are ethylideneimine via a 1,2 hydrogen shift, N-methyl methyleneimine via a 1,2 methyl shift, and the corresponding aziridine by cyclization. The three reactions have been studied by the semiempirical MNDO method. The charge transfer effects have been investigated. Theoretically calculated vibrational frequencies and kinetic properties have been used in calculating macroscopic thermodynamic and kinetic properties. The entropies of activation, the high pressure rate constants, k_∞, and the high pressure Arrhenius parameters, A_∞ and E_∞, have been computed. The kinetic isotope effects have also been studied.     

Azacrownlactams Derived from Biphenyl. Study of Their Conformations, Complexation Ability and Electrochemical Behavior

Several macrolactams containing in their structure biphenyl and pyridine moieties have been synthesized. The complexation ability of these compounds has been evaluated and the results have been explained considering the existence of intramolecular hydrogen bonds. Conformational studies have been developed in some cases. Single-crystal X-ray diffraction studies have been carried out with one of the ligands. The electrochemical response of ligands 1 and 3 has been studied using cyclic and square wave voltammetry. The interaction of these ligands with Cu²⁺ ions in CH₃CN has been investigated by electrochemical techniques.     

Physicochemical studies on the micellization behavior of cetylpyridinium chloride and triton X-100 binary mixtures in aqueous medium

Physicochemistry of micellization of binary mixtures of cetylpyridinium chloride (CPC) and Triton X-100 (TX-100) have been investigated and the data collected have been analyzed and correlated. Tensiometric, conductometric, spectrophotometric, calorimetric and polarographic methods have been employed in the study. Parameters like critical micellar concentration (CMC), counter-ion binding, energetics of micellization, interfacial surfactant adsorption and minimum area of amphiphile head groups at CMC have been determined. The diffusion coefficients of pure and mixed micelles in solution have been determined by the polarographic method. The regular solution theory of Rubingh has been considered to get information on the micellar composition and their mutual interaction (synergistic for the studied system) in solution. The packing of the monomer in micelle has been estimated to witness spherical geometry for CPC and its mixtures with TX-100, whereas the later has been found to be spheroidal. Polarographic measurements have evidenced comparable diffusion coefficients of CPC and TX-100 micelles whereas their mixed micelles have shown lower values with a minimum, at equimolar composition.     

Lipids of the fruit of Pyrus communis

The compositions of the various groups of liposoluble compounds in the peel and flesh of the fruitPyrus communis of the varieties Williams and Bere Ardanpon have been established and their amounts have been determined by chromatographic and chemical methods. The qualitative compositions have been shown to be identical and characteristic quantitative differences have been found in the lipids of individual elements of these pairs. The fatty acid compositions of the lipids have been studied.M. V. Lomonosov Technological Institute of the Food Industry, Odessa, Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 175–180, March–April, 1989.     

Non-symmetrical discotic liquid crystalline dimers: molecular design,synthesis and mesomorphic properties‡

The synthesis and mesomorphic properties of novel non-symmetrical discotic dimers have been investigated. Dimers have been prepared by the combination of electron-deficient (n-type) anthraquinone and electron-rich (p-type) triphenylene discotic monomers. The mesophases have been characterised using polarising optical microscopy, differential scanning calorimetry and X-ray diffraction. Most of the dimers have been shown to exhibit a rectangular columnar mesophase and one has a nematic columnar mesophase also. Charge transfer behaviour has been studied by UV–Vis spectroscopy.     

Curing of an epoxy resin modified with poly(methylmethacrylate) monitored by simultaneous dielectric/near infrared spectroscopies

Simultaneous dielectric and near infrared measurements have been performed in “real-time” to follow polymerisation reactions on blends of a diglycidyl ether of bisphenol-A epoxy resin with 4,4^′-diaminodiphenylmethane hardener and different amounts of poly(methylmethacrylate) as modifier. The effect of the modifier amount on the polymerisation reactions has been studied, as well as that of the curing temperature. Epoxy and amine conversions have been followed by near infrared spectroscopy (NIR), while changes in molecular mobility in the reaction mixture have been analysed by dielectric relaxation spectroscopy (DRS). Evolutions of ionic conductivity and α-relaxation have been analysed and vitrification times have been obtained. The relaxational behaviour has been analysed through curing in the frequency domain, being the change of the main relaxation indicative of the cure reaction advancement. DRS data are also presented as complex impedance Z(ω). Vitrification times, obtained by dielectrometry have been compared with those obtained by rheological measurements and gelation times obtained by NIR have been compared with those obtained by solvent extraction.     

Laser-induced Fluorescence and Dispersed Fluorescence Spectroscopy of NiB: Identification of a New 2II State in 19000-22100 cm-1

The laser-induced fluorescence excitation spectra of jet-cooled NiB radicals have been recorded in the energy range of 19000-22100 cm^-1. Eleven bands have been assigned to the [20.77]²II-X²∑⁺ transition system for the first time. The dispersed fluorescence spectra related to most of these bands have been investigated. Vibrationally excited levels of the ground electronic state, with v" up to 6, have been observed. In addition, the lifetimes for almost all the observed bands have also been measured.     

The laser Raman and infrared spectra of crystalline dibenzyl

The Raman spectrum of crystalline dibenzyl has been excited with a 50-mw He-Ne laser (6328 Å) and thirty one Raman bands have been recorded. The far infrared spec trum which reveals six absorptions in the 10–270 cm⁻¹ region and the infrared spectrum from 300–3200 cm⁻¹ have been observed, and correlations with the Raman frequencies have been established. Assignments of some of the characteristic frequencies have been made, and the implications of the data regarding the geometry of the molecule are discussed.     

Effect of the Porphyrin Structure on the Kinetics of Complex Formation with Zinc Dipyrromethene in Dimethylformamide

The kinetics of complex formation of zinc dipyrromethene with tetraphenylporphyrin, octaethylporphyrin, and 5,15-dipentyl-2,3,7,8,12,13,17,18-octamethylporphine at 368–420 K have been studied. The kinetic parameters (k _app, k _v) of the complex formation processes have been determined. The porphyrin molecules have been optimized by the PM3 quantum-chemical method, and their geometric characteristics have been obtained. The effect of the structure and macrocycle strain of porphyrins on the complex formation rate is discussed.     

Viscosity and Thermodynamics of Viscous Flow of 1-propanol with Aniline,N-methylaniline and N,N-dimethylaniline

Abstract

Viscosities of the systems, 1-propanol + aniline, 1-propanol+N-methylaniline and 1-propanol+N,N-dimethylaniline have been measured in the temperature range 294.15 to 323.15K for the whole range of composition. The viscosities have been plotted against mole fraction of anilines. The viscosity-composition curves show minima, though not well-defined, in highly rich, moderately rich and moderately poor regions of 1-propanol respectively for 1-propanol + aniline, 1-propanol + N-methylaniline and 1-propanol +N,N-dimethylaniline systems. The excess viscosities have been found to be negative for all the systems throughout the whole composition and plotted against mole fraction of anilines. The thermodynamic activation parameters, such as, enthalpies, entropies and free energies and their excess values have been evaluated. The excess free energies have been found to be negative for all the systems and over the whole range of composition. The excess free energies have been plotted against the mole fraction of anilines. The viscosities, excess viscosities and excess free energies have been explained by assuming that the associated compounds, aniline, N-methylaniline and 1-propanol, are dissociated into smaller units in the solution systems by the rupture of H-bonds.     

Berberis alkaloids. XXV. Structures of bernumidine and bernumicine

The alkaloid compositions of young shoots and leaves ofBerberis nummularia Bge. have been studied. The new alkaloids bernumidine (II) and bernumicine (III) have been isolated from the leaves, and their structures have been established.     

Volumetric studies and thermodynamics of viscous flow of hydroxamic acids in acetone + water solvent at temperatures 303.15 and 313.15 K

Densities ρ and viscosities η of two hydroxamic acids, N-phenyl-2-chlorobenzo- and N-o-tolyl-4-chlorobenzo-, have been determined as a function of their concentration in aqueous acetone solution at temperatures 303.15 and 313.15 K. Apparent molar volumes, standard-state partial molar volumes and relative viscosities have been calculated. The viscosity data have been analyzed using Jones-Dole equation. The activation thermodynamic parameters of viscous flow have been evaluated using Feakins equation. These were obtained to throw light on the mechanism of viscous flow. Thermodynamic interactions in solutions have been studied in terms of a number of excess functions calculated from the experimental data. The effect of hydroxamic acid concentration and temperature on these parameters has been discussed. The results were interpreted in the light of solute-solvent interactions in aquo-organic media.     

Dynamic-mechanical properties and melting points of some aliphatic and partially aromatic polyamides

Some aliphatic and partially aromatic polyamides have been prepared from hexamethylene diamine and the following dicarboxylic acids: deca-, octa-, hexa-methylenedicarboxylic, p-carboxymethylphenoxyacetic, p-carboxyethylphenoxyacetic, p-phenylenedipropionic, p-phenylenediacetic, p-carboxymethoxyphenoxyacetic, β(p-carboxymethyl)phenylpropionic.The dynamic-mechanical properties at 110 Hz have been measured between ?140° and about 200. Three relaxation processes α β and γ have been found: only the main transition α appreciably depends on chemical structure.The influences of the length of repeating unit and of in-chain substitution on melting points, crystallinity and the dynamic-mechanical α transition have been investigated. The results have been discussed in terms of chain flexibility, chain packing and intermolecular forces.     

Surface-ionization mass spectrometry of terpene hydrocarbons

The surface ionizations of four terpene hydrocarbons (α-pinene, alloocimene, Δ³-carene, and limonene) on oxidized tungsten wires and ribbons have been investigated. The mass spectra of the ions and the temperature dependences of the currents have been obtained, current densities have been estimated, and monomolecular decompositions of the metastable vibrationally excited ions have been found. The actions on the surface of oxidized tungsten leading to the formation of ionizing particles are considered. The ionizing potentials of the radicals (M - H) obtained on the splitting out of hydrogen atoms from the molecules have been estimated.