Zinc reaction with diphenylantimony and diphenylbismuth chlorides in aprotic solvents

Products of zinc oxidation with diphenylantimony and diphenylbismuth chlorides in aprotic solvents are established. The effective adsorption constants of the reagents on the metal surface and the rate constants and activation energies of the processes under study are calculated.     

Oxidation of magnesium with carbon tetrachloride in aprotic solvents

Formal kinetic regularities and the end products of oxidation of magnesium with carbon tetrachloride in the environment of dipolar aprotic solvents were revealed. The effective equilibrium constant, enthalpy and entropy of adsorption of carbon tetrachloride and N,N-dimethylformamide at a metal surface, the rate constant and activation energy of the investigated reaction were determined. The effect of temperature on the dependence of the process on the donor properties of the used coordinating solvents was established and justified. A probable scheme of the process was suggested.     

Oxidation of magnesium with cyclopentadienyl(triphenylphosphine)nickel chloride in aprotic solvents

The products of magnesium oxidation with cyclopentadienyl(triphenylphosphine)nickel chloride were revealed. Effective equilibrium constants of adsorption of the reagents on the metal surface, entropy and enthalpy of these processes, rate constants, and activation energy were determined. A probable scheme of the process is assumed.     

Capsule-like assemblies in polar solvents

Calix[4]arene derivatives with four anionic groups at their upper rim form discrete 1:1 complexes with complementary calix[4]arene derivatives bearing four cationic groups at their upper rim. Each cation is bound by two anions, and vice versa, in a mutual chelate arrangement, reinforced by a network of ionic hydrogen bonds. These multiple electrostatic interactions lead to the formation of highly stable capsule-like assemblies even in polar protic solvents such as methanol and water. In the capsule interior a cavity is formed that is in principle large enough for the encapsulation of small aliphatic and aromatic guests (170-230 A(3)). Monte Carlo simulations in water reproducibly lead to the same regular opimized structures. These differ mainly by their inner volume and flexibility, as demonstrated by molecular dynamics calculations. Most half-spheres can be synthesized by way of the tetrakis(chloromethyl) or the tetrabromocalix[4]arene intermediate. Oppositely charged calix[6]arenes also form strong complexes, but no indication was found for a lock in the cone conformation. The formation of the ball-shaped complexes from calix[4]arene building blocks was studied with Job plots, NMR titrations, NOESY, and variable-temperature experiments, as well as ESI-MS measurements. Investigations aimed at the inclusion of various guest molecules were carried out with alcohols, sulfoxides, benzene derivatives, and ammonium, as well as pyrazinium guests. Although binding isotherms were generated with cationic guests, these must be considered to be loosely associated around the seam rather than included inside the capsule.     

Dispersion polymerization in polar solvents

The effect of the nitrogen purge, monomer purification, type of agitation, and presence of costabilizer on the particle size distribution (PSD) was investigated in the dispersion po-lymerization of styrene in ethanol and in the dispersion copolymerization of styrene and butyl acrylate in a water–ethanol mixture. Purging with nitrogen and, to a lesser extent, monomer purification, were of paramount importance to achieve monodispersity. The type of agitation had a week effect on the PSD, whereas the presence of costabilizer had no effect on the PSD. © 1995 John Wiley & Sons, Inc.     

Alkylation of magnesium enamide with alkyl chlorides and fluorides

A magnesium enamide derived from N-2-(N',N'-diethylamino)ethyl imine reacts with a primary and secondary alkyl chloride or a primary alkyl fluoride to give an alpha-alkylated ketone in good to excellent yield after hydrolysis. The reaction takes place with a high level of inversion of stereochemistry at the electrophilic carbon center and will be useful for production of optically active compounds.     

Complexes of acid amides with polar aprotic solvents

Solid complexes of bis(N-phenyl)-pyromellitic acid amide with equimolar binary mixtures of dimethylformamide, dimethylacetamide, dimethylsulfoxide and N-methylpyrrolidone were prepared and studied by evolved gas analysis using mass spectrometry. The activity sequence of these compounds in forming complexes with bis(N-phenyl)-pyromellitic acid amide was established.     

Complexes of acid amides with polar aprotic solvents

A study was made of the effects of organic carbonyl-containing compounds and inorganic acids on the character of complex formation of the solvent with polyacid amides, and in particular on the frequency of three-dimensional networks formed by hydrogen-bonds in solid polyacid amide films. It was found that the characteristics of the solid-phase cyclodehydration process can be varied within a wide range by means of active additives.

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Zusammenfassung Die Wirkung von organichen carbonyl-enthaltenden Verbindungen und anorganischen Säuren auf den Charakter der Komplexbildung von Lösungsmitteln mit Polysäureamiden wurde untersucht, inbesondere was die Häufigkeit von dreidimensionalen, durch Wasserstoffbindungen in den festen Polysäureamidfilmen zustande kommenden Vernetzungen betrifft. Es wurde festgestellt, daß die Kennwerte des Cyclodehydratisierungsprozesses in fester Phase innerhalb weiter Grenzen durch aktive Additive variiert werden können.

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Complexes of amic acids with polar aprotic solvents

The polymer-polymer interactions of a polyamic acid (PAA) with polybases (polyvinylpyrrolidone, polyacrylonitrile and polyvinylpyridine) were studied by means of massspectrometric thermal analysis (MTA), TG, DTA and IR-spectroscopic methods in solution and in the solid state. The polybases were shown to substitute the solvent from its complex with PAA, forming H-bonds or salt-type polycomplexes with PAA. The MTA method proved to be very informative for the investigation of interpolymer interactions in the solid state.

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Zusammenfassung Mittels MS-Thermoanalyse (MTA), TG, DTA und IR-Spektroskopie wurden sowohl in Lösung als auch im festen Aggregatzustand die Polymer-Polymer-Wechselwirkungen zwischen Polyamicsäure (PAA) und Polybasen (Polyvinylpyrrolidon, Polyacrylnitril und Polyvinyl-pyridin) untersucht. Polybasen ersetzen das Lösungsmittel in seinem Komplex mit PAA und bilden dabei mit PAA Wasserstoffbindungen oder salzähnliche Polykomplexe. Die MTA-Methode erwies sich bei der Untersuchung von interpolymeren Wechselwirkungen im festen Aggregatzustand als sehr informativ.

     

Complexes of amic acids with polar aprotic solvents

The nonisothermal kinetics of solid-phase cyclodehydration of poly(4,4'-oxydiphenylene) pyromellitamic acid has been investigated with the aid of mass-spectrometric thermal analysis. It was established that depending on the method of preparation of the samples, the kinetics of cyclization vary from the polychromatic (film) to the monochromatic (fiber) kinetics. The possibility of the catalysis of the process as a result of the formation of complexes between the polymer and imidazole and its substituents is shown.

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Zusammenfassung Mittels massenspektrometrischer Thermoanalyse wurde die nichtisotherme Kinetik der Cyclodehydratation von Poly(4,4'-Oxydiphenylen)pyromellithsäure im festen Zustand untersucht. Es wurde festgestellt, daß die Cyclisationskinetik in Abhängigkeit vom Herstellungsverfahren der Proben von polychromatisch (Film) bis monochromatisch (Fiber) variiert. Die Möglichkeit der Katalyse des Vorganges infolge von Komplexbildung zwischen Polymer und Imidazol und seiner Substituenten wird gezeigt.

     

Selenophilic reaction of organolithium and magnesium reagents with phosphinoselenoic chlorides

The reaction of phosphinoselenoic chlorides 1 with various organolithium and magnesium reagents was studied. Sequential reaction of phosphinoselenoic chlorides 1 with organolithium and magnesium reagents and elemental selenium gave two types of products, phosphine selenides 2 and phosphinodiselenoic acid esters 3 . The esters 3 appeared to be formed via the selenophilic reaction of organolithium and magnesium reagents with the chlorides 1 . Molecular orbital calculations were carried out for model compounds H₂P(E)Cl (E = O, S and Se) to determine their electronic structures. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:185–191, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20091     

Complexation of 6-hydroxyquinoline with trimethylamine in polar and non-polar solvents

Spectral characteristics of 6-hydroxyquinoline (6-HQ) in presence of trimethylamine (TMA) were investigated in polar and non-polar solvents. The steady-state absorption, emission and excitation spectra along with the transient parameters reveal a strong ground state hydrogen-bonded complex formation between the 6-HQ and TMA molecules in both the media. A large Stokes shifted emission due to the formation of contact ion-pairs is observed in these media. However, in acetonitrile the longer decay time (≈12 ns) with relatively broadened emission spectra can be attributed to the presence of solvent separated ion-pairs in addition to contact ion-pairs. The ground state equilibrium constant for complex formation has been determined. The observed quenching behaviour of the fluorescence emission from the normal molecule with TMA appears to be static in nature.     

Reactions of 1,2,3-triphenylcyclopropene with N-bromosuccinimide in various polar solvents

Conclusions A study was made of the reactions of 1,2,3-triphenylcyclopropene with N-bromosuccinimide in alcohol, acetic acid, aqueous DME, and also anhydrous DMSO. The direction and stereochemistry of these reactions were established.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 234–237, January, 1977.     

Self-assembly of molecular capsules in polar solvents

[structure: see text] We present a novel type of molecular capsule formed by self-organization of calix[4]arenes with several oppositely charged functional groups located at their upper rims. In highly polar solvents, the complementary half-spheres form stable 1:1 complexes with association constants of up to 7 x 10(5) M(-)(1) in methanol. The cavity inside the capsules is large enough for the inclusion of small aliphatic or (hetero)aromatic guest molecules.     

Time-resolved interaction of polar solvents with excited pyrylium cations

The time-resolved fluorescence spectra of two pyrylium-ion derivatives have been investigated. In the temperature range 77 to 190 K, a red-shift of the fluorescence spectra of the order of 25–70 nm is observed and assigned to a fast solvent relaxation process. Time-resolved experiments carried out at 160 K showed a rapid decrease of the emission from the non-relaxed excited state at short wavelengths and a corresponding build-up of the emission of the relaxed one at longer wavelengths. At 120 K emission from the non-relaxed electronic state is predominant.     

Confinement of polar solvents within beta-cyclodextrins

Using molecular dynamics techniques, we examined equilibrium and dynamical characteristics pertaining to the solvation of a single beta-cyclodextrin (CD) in water and in dimethylsulfoxide (DMSO). Compared to its global minimum structure, the overall shape of the solute in solution is reasonably well preserved. While in aqueous solutions, the average number of solvent molecules retained within the central cavity of the oligosaccharide is close to 5, for DMSO, that number reduces to approximately 1. No evidence of significant orientational correlations of the trapped molecules were found in either solvent. The main contributions to the hydrogen-bond (HB) connectivity between the solute and the bulk phases are due to the more distal HO6-O6 hydroxyl groups, acting as HB donors and acceptors. The average residence time for retained DMSO was found to be in the nanosecond range, and it is, at least, 1 order of magnitude longer that the one observed for water. We also analyzed the characteristics of the solvation of the beta-CD in an equimolar water-DMSO mixture. In this environment, we found a preferential localization of a single DMSO molecule in the interior of the CD and a very minor retention of water. In the mixture, the characteristic time of residence of the trapped DMSO molecule increases by a factor of approximately 2. The observed difference was rationalized in terms of the fluctuations of the local concentrations of the two species in the vicinity of the CD top and bottom rims.     

Hydrogen-bonded capsules in polar,protic solvents

A kinetically stable, dimeric capsule is formed by tetrahydroxyresorcinarene in methanol; it encapsulates tropylium and tetramethylammonium cations.