Recent progress in tartaric acid‐modified Raney nickel system for enantio‐differentiating hydrogenation

Tartaric acidmodified Raney nickel (TAMRNi) is an enantiodifferentiating catalyst for hydrogenation of ketones. The stereochemical models explaining the enantiodifferentiation of ketoester and 2alkanone were unified as an extended stereochemical model by the experimental supports. Based on this new model, a working hypothesis to improve the enantiomeric excess (ee) of the ketoester/TAMRNi system was developed, and the ee was improved to 96%. By further fine tuning of this system, almost perfect enantiodifferentiation resulting in over 98% ee was achieved.     

Influence of F and CF3 Groups at the C=C Double Bond on the Structure and Properties of Olefinic‐Series Compounds in the Gas Phase: an ab initio MP2 Study

Ab initio calculations of gasphase fluoroolefins with F or CF₃ groups as substituents at the C=C double bond were performed using secondorder Möller–Plesset perturbation theory (MP2) with the 6–31G^* and augccpVDZ basis sets and full geometry optimization. Geometrical parameters, singleelectron energies, electrondensity distributions, dipole moments, polarizabilities, and hyperpolarizabilities were computed. Variations in the electronic structure of fluoroolefins were analyzed and compared with variations in their physicochemical properties and reactivity.     

Generalization of the fourth‐order Hylleraas functional for the case of a non‐Hermitian unperturbed Hamiltonian

Generalization of the fourthorder Hylleraas functional form have been performed for the case of nonHermitian operators. Our new formulas are relevant when the Hermitian Born–Oppenheimer Hamiltonian is decomposed into a nonHermitian unperturbed part and also a nonHermitian perturbation. The results can be used to develop BSSEfree intermolecular perturbation theory up to fourthorder.     

Distortion of the Cucurbituril Molecule by an Included 4‐Methylpyridinum Cation

The crystal and molecular structures of a guest–host complex of cucurbituril with 4methylpyridinium, {(4MePyH) (C₃₆H₃₆N₂₄O₁₂)}(NO₃) · 4H₂O, were determined by Xray structural analysis. The crystals are monoclinic with a = 26.276(3) , b = 25.861(2) , c = 17.375(2) , = 124.17(1)°, V_cell =9768.6(18) ³, space group Cc, and Z = 8. The structure contains two crystallographically independent supramolecular complexes. They are arranged in pillars oriented along the a axis. In each pillar, the complexes are parallel to each other. The pillars are shifted with respect to each other by onehalf of the crystallographic translation. The centers of the supermolecules are arranged according to a pseudobodycentered motif. Distortions of the cucurbituril molecule depending on the guest type have been analyzed with the use of results obtained in the present and previous studies.     

Proton Magnetic Resonance and Molecular Simulation in Configurational and Conformational Analysis of Cyclohexanone Derivatives

Developing the previously tested approach to the configurational and conformational analysis of cyclic chiral compounds based on a complex use of NMR spectra and molecular simulation, we determined the configuration 1R, 2R, 4R, 1S and conformational state of 2[1hydroxy1(4carbomethoxyphenyl) methyl]pmenthane3one, a minor product of the directed aldol reaction of (–)menthone with 4carbomethoxybenzaldehyde. The configurations of the cyclic chiral centers were determined by analysis of the spin–spin coupling constants of the protons of the cyclohexanone ring for the most probable conformations of alternative stereoisomers. The S configuration of the C (1) exocyclic chiral center was established from the different orientation of the benzene ring relative to the cyclohexanone fragment in alternative stereoisomers, as shown by semiempirical quantumchemical simulations (AM1 and PM3 methods), and from the observed difference in proton chemical shift between the examined hydroxyketone and the model (+)isomenthone (1R, 4Rdiastereomer).     

35Cl NQR Studies of the Geometry of Aromatic Imines

The preferred conformation of solidphase R4benzylidene3,4dichloroaniline molecules has been established by nuclear quadrupole resonance (NQR) combined with quantum chemical calculations. The conformational effect of substitutes reported previously is proved. The rotation angle of the plane of the aniline ring with respect to the plane of the azomethine bond is given.     

Two‐dimensional step‐scan FTIR: a tool to unravel the OH‐valency‐range of the spectrum of Cellulose I

This article presents the results of the first application of dynamic mechanical analysis (DMA) coupled with 2D stepscan Fourier transform infrared (FTIR) spectroscopy, to cellulose. It is demonstrated that the broad hydroxyl infrared absorption band between 3700 and 3000cm^–1 in the cellulose infrared spectra could be separated into distinct bands by this dynamic rheooptical investigation using FTIRspectroscopy as detecting system. The responses of the OHgroups to an external perturbation were recorded as inphase and outofphase spectra. The cross correlation of these spectra gave the 2D synchronous and asynchronous plots, which showed clearly separated bands in the OHvibration range and the relation of the OHgroups to each other. It is demonstrated that it is possible to establish relations between the OHbands and the cellulose structure.     

The Chemistry of Methane Remediation by a Non‐thermal Atmospheric Pressure Plasma

The destruction of methane by a nonthermal plasma in atmospheric pressure gas streams of nitrogen with variable amounts of added oxygen has been investigated. The identities and concentrations of the endproducts are determined by online FTIR spectroscopy and the plasma chemistry is interpreted using kinetic modelling. For a deposited energy of 118 kJ m^–3, the destruction is 12% in nitrogen decreasing monotonically to 5% in air. The major endproducts are HCN and NH₃ in nitrogen and CO, CO₂, N₂O, NO and NO₂ for gas streams containing oxygen. The chemistry in pure nitrogen is predominantly due to reactions of electronicallyexcited nitrogen atoms, N(²D). The addition of oxygen converts the excited state nitrogen into nitrogen oxides reducing the methane destruction which then arises by O and OH reactions yielding CO and, to a lesser extent, CO₂. The modelling correctly predicts the magnitude of the methane destruction as a function of added oxygen and the concentrations of the endproducts for processing in both nitrogen and air.     

Structure and Magnetic Properties of Solid Solutions of Molecular Magnetics Based on Ni(II) and Co(II) Complexes with Nitroxyl Radicals

Ni(II) and Co(II) complexes with deprotonated paramagnetic enaminoketones 4(3,3,3trifluorine2oxopropylidene) 2,2,5,5tetramethyl3imidazolidine1oxyl (L) and 4(3,3,3trifluorine1chlorine2oxopropylidene)2,2,5,5tetramethyl3imidazolidine1oxyl (L¹) and alcohols are shown to form continuous solid solutions Ni_xCo_1-xL₂(C₂H₅OH)₂ and Ni_xCo_1-xL₂ ¹(CH₃OH)₂. Single crystal Xray diffraction analysis showed that concentration variation practically does not affect the structural characteristics of the solid solutions. Distinguishing features if the magnetic behavior of Ni_xCo_1-xL₂ · (C₂H₅OH)₂ and Ni_xCo_1-xL₂ ¹(CH₃OH)₂ are the antiferromagnetic interaction of the moments of the nickel and cobalt sublattices inside the polymeric layers and the antiferromagnetic nature of interlayer interaction of the magnetic moments.     

Structure of 2,4,4,5,5‐pentamethyl‐2‐imidazoline‐1‐oxyl‐3‐oxide

The crystal and molecular structures of the stable nitroxide radical 2,4,4,5,5pentamethyl2imidazoline1oxyl3oxide was determined. The N—O bond lengths are 1.279(2) and 1.280(2), respectively. The O^-—N⁺=C—N— O fragment is nearly planar with carbon atoms of the ethyl fragment that deviated from the O—N⁺=C—N—O plane by –0.204(5) and +0.176(5). The minimum intermolecular distance between the oxygen atoms of NO groups is 4.094.     

Crystal Structure Study of the Metastable β-modification of Glycine and its Transformation into the α-modification

Crystal structure refinement was performed of the metastable modification of glycine (space gr. P2₁, a = 5.092(2) , b = 6.273(3) , c = 5.384(3), = 113.17(4)°, Z = 2, R = 0.0274). The crystals were obtained by a new method (not described in the literature): they were precipitated from a water solution with the addition of glacial acetic acid. The crystal structure of the glycine modification [space gr. P2₁/n, a =5.106(1) , b = 11.979(5) , c = 5.463(2) , = 111.75(2)°:, Z =4] was refined for comparison. Transition from the to the modification in a damp atmosphere was revealed, resulting in the formation of a strongly strained crystal of a mosaic structure. The orientation of the crystallographic axes in the newly formed crystal of the modification relative to the axes in the initial crystal of the modification was determined. It is shown that as in glycine, the lengths of the intramolecular C—O bonds in the modification are fairly similar [1.248(2) and 1.253(2) ] and the previously found significant difference between them is most likely due to the errors of the photomethod. A comparative analysis of the crystal structures of the and glycine modifications (glycine zwitterion packings and structure of intermolecular hydrogen bond networks) was performed. Data of the analysis are used to discuss the properties of the glycine modifications, the possible reasons for the stability of the modification in dry air, the difficulties of crystal growth from solutions, and the ease of crystallization of the modification under various conditions.     

Separation of microamounts of yttrium from strontium in the two‐phase water/nitrobenzene system

A rapid and very effective separation of carrierfree 90 Y in the aqueous phase of the water/nitrobenzene system from an 90 Y/90 Sr generator is proposed. After a twostage extraction separation, the radionuclide impurity of 90 Sr in the final aqueous phase containing carrierfree 90 Y is approximately 10 16%, while the chemical yield of 90 Y in this phase is practically 100%.     

Effect of Oxygen Redistribution on the Normal and Superconducting Properties of Yttrium High‐Temperature Superconductors

An anomaly is found in the vicinity of T_max 560$ K on electric resistance versus temperature curves for yttrium hightemperature superconductors of the 123 phase. Xray phase analysis suggests a structural phase transition in the vicinity of T_max due to oxygen redistribution in the mobile sublattice of this compound. Investigation of samples with Y partially replaced by Ca has shown that the structural phase transition does not depend on carrier concentration in the conduction band.     

Crystal and Molecular Structure of 2,3‐Pentamethylene‐3,4‐Dihydroquinazolone‐4 Nitrate. Conjugation Effects in the Series of Tricyclic Quinazolines

The structure of 2,3pentamethylene3,4dihydroquinazolone4 nitrate was determined by means of Xray diffraction. Analysis was performed of the geometry of the heterocyclic ring in 2,3tri, tetra, and pentamethylene3,4dihydroquinazolones4, quinazolines, and their salts with inorganic acids and complexes with metal ions. It is found that in the N(1)—C(2)—N(3) fragment in the bases of quinazolines and quinazolones4, the conjugation is less pronounced than that in the protonated (salt) forms.     

Additive telluromolybdates. Structure and catalysis in oxidation

Additive telluromolybdates, MoO₃·2TeO₂ and M^IIO·TeO₂·MoO₃ (M^IITeMoO₆; M^II = Co, Mn, Zn), converted ethyl lactate selectively to pyruvate in a vaporphase fixedbed flow system at 250–300 °C. A synergy in activity was observed for binary TeO₂–MoO₃, and crystalline Te₂MoO₇ was suggested as the active species. The Rietveld analysis of powder XRD patterns of ternary CoTeMoO₆ revealed the layer structure quite different from that of the reference Te₂MoO₇, but tellurium was again located adjacent to molybdenum linked through lattice oxygen.     

A family of P-stable exponentially‐fitted methods for the numerical solution of the Schrödinger equation

A family of Pstable exponentiallyfitted methods for the numerical solution of the Schrödinger equation is developed in this paper. An application to the resonance problem of the radial Schrödinger equation indicates that the new method is generally more efficient than the previously developed exponentiallyfitted methods of the same kind.     

Crystal Structures of [Ni(Phen)(i‐Bu2PS2)2] and [Ni(Phen)3](i‐Bu2PS2)2 Complexes and Interaction between Coordinated 1,10‐Phenanthroline Molecules

Single crystals of [Ni(Phen)(iBu₂PS₂)₂] (I) and [Ni(Phen)₃](iBu₂PS₂)₂ (III) compounds were grown, and their structures were determined by Xray diffraction analysis (CAD4 diffractometer, MoK radiation, 3336 F _hkl , R = 0.0373 for I and 2575 F _hkl for III). The crystals of complex I have a triclinic unit cell with the following parameters: a = 11.097(1) , b = 14.903(2) , c = 22.650(3); = 75.18(1)°, = 80.50(1)°, = 75.07(1)°, V = 3479.2(7)³, Z = 4, _calc = 1.255 g/cm³, and space group 1; the crystals of III have a monoclinic unit cell with the following parameters: a = 19.010(3), b = 15.481(1) , c = 17.940(3); = 97.58(1)°, V = 5233.5(12)³, Z = 4, _calc = 1.292 g/cm³, and space group C2/c. The structure of complex I is built from mononuclear molecules, and the structure of III, from [Ni(Phen)₃]²⁺ complex cations and i Bu₂PS₂ ^- outersphere anions. The NiN₂S₄ coordination polyhedra in the structure of I and NiN₆ in the structure of III are distorted octahedra. Based on structural data, the interaction between the coordinated Phen molecules of complexes I, [Ni(Phen)₂(iBu₂PS₂)](iBu₂PS₂) (II), and III is considered, as well as the packing modes of these complexes.     

Conformational Analysis of IR Spectra of Alkyl and Fluoroalkyl Cyclohexanecarboxylic Acids

IR spectra were simulated for a series of alkyl and fluoroalkyl cyclohexanecarboxylic acids, whose experimental spectra have been previously recorded in the temperature range 77–500 K. The simulation was performed taking into account the conformational mobility of the molecules and a decrease in the hydrogenbond energy of Hcomplexes during heating. It has been shown that temperatureinduced changes in the spectra are caused by conformational transitions accompanied by rotation of alkyl/fluoroalkyl and or carboxyl groups and a decrease in hydrogebond energy during heating.