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.     

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.     

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.     

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.     

Phase Transitions in Channel Clathrates of Thiourea with Hexachloroethane and Tetrachloroethane

An explanation is proposed for the nature of phase transitions in channel clathrates of thiourea with hexachloroethane and tetrachloroethane. Analysis of experimental temperature dependences of specific heat, entropy, and NQR spectra indicates the existence of first and secondorder phase transitions. In the thiourea + hexachloroethane compound, the secondorder phase transition (94.60 K, entropy gain Rln2) implies a transformation of two equiprobable states (lowtemperature phase) into a single new state (hightemperature phase). The firstorder phase transition corresponds to clathrate channel distortion. In the thiourea + tetrachloroethane compound, the secondorder phase transition (224K, entropy change Rln 6) occurs with transformation of six equiprobable states (lowtemperature phase) into a single new state (hightemperature phase). The firstorder phase transition corresponds to clathrate channel distortion. The next secondorder phase transition observed in this compound at 248 K leads to disappearance of the four possible orientations of guest molecules in the clathrate channel of hexagonal section and to a transition of guest molecules to chaotic orientation (entropy increment equals Rln 4).     

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.     

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.     

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.     

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%.     

Reaction characteristics of cellulose in the LiCl/1,3‐dimethyl‐2‐imidazolidinone solvent system

In order to elucidate the nature of the LiCl/1,3dimethy2imidazolidinone (DMI) solvent system as one of the homogeneous reaction media of cellulose, cellulose acetate (CA) and Omethylcellulose (MC) were prepared using this solvent system, and the distribution of substituents within anhydroglucose units was examined by ¹³CNMR. It was found that (i) homogeneous cellulose solutions can be easily prepared by heating 2, 5–12 and 100 parts of weight of cellulose, LiCl, and DMI, respectively, and (ii) the relative reactivity of hydroxyl groups is in the order C6 > C2 > C3 for both CA and MC. A remarkable feature of this solvent system is that the reaction efficiency in etherification is very high compared with other homogeneous solvent systems.     

Crystal and Molecular Structure of Monoammonium Salt of 5‐nitroaminotetrazole

Xray structural investigation of the monoammonium salt of 5nitroaminotetrazole was performed. The crystals are orthorhombic: a = 10.077(1), b = 17.009(1), c = 6.6472(6), V = 1139.33(17)³, space group Pbca, Z =8, _calc = 1.715 g/cm³. Monodeprotonation of 5nitroaminotetrazole during formation of the salt occurs at the N(4) nitrogen atom of the heterocycle. The anion has an almost flat structure; the bond lengths suggest delocalization of electron density in the molecule. The negative charge is distributed among three nitrogen atoms and two oxygen atoms of the anion. Changes in the geometrical parameters of 5nitroaminotetrazole on monodeprotonation are considered.     

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.     

Temperature-programmed desorption (TPD) of hydrogen from a NiNaY zeolite after reduction

By TPD it could be shown that hydrogen desorption of a reduced NiY-zeolite stoichiometrically corresponds to the decrease of reduction degree. Therefore, the reason for hydrogen abstraction should be a partial reoxidation of Ni⁰.

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, NiY- . Ni⁰.

     

Structure and Conformational Mobility of 4′‐Pentyl‐4‐Cyanobiphenyl from IR Spectroscopic Data

The structure and conformational mobility of 4pentyl4cyanobiphenyl in the liquid and liquidcrystal states were investigated by means of IR spectroscopy (experiment and theory). IR absorption spectra in the frequency range 400–4000 cm^-1 were measured in the temperature range 26–150°. Theoretical simulation of the IR spectra was performed using the fragment approach. A comparison of theoretical and experimental spectra showed that the examined samples were mixtures of conformers; characteristics of the most probable conformers are given. Temperaturerelated changes in the spectrum are due to the conformational mobility of the molecules, which is not high in the temperature range considered.     

General foundations of high‐dimensional model representations

A family of multivariate representations is introduced to capture the input–output relationships of highdimensional physical systems with many input variables. A systematic mapping procedure between the inputs and outputs is prescribed to reveal the hierarchy of correlations amongst the input variables. It is argued that for most welldefined physical systems, only relatively loworder correlations of the input variables are expected to have an impact upon the output. The highdimensional model representations (HDMR) utilize this property to present an exact hierarchical representation of the physical system. At each new level of HDMR, higherorder correlated effects of the input variables are introduced. Tests on several systems indicate that the few lowestorder terms are often sufficient to represent the model in equivalent form to good accuracy. The input variables may be either finitedimensional (i.e., a vector of parameters chosen from the Euclidean space ) or may be infinitedimensional as in the function space . Each hierarchical level of HDMR is obtained by applying a suitable projection operator to the output function and each of these levels are orthogonal to each other with respect to an appropriately defined inner product. A family of HDMRs may be generated with each having distinct character by the use of different choices of projection operators. Two types of HDMRs are illustrated in the paper: ANOVAHDMR is the same as the analysis of variance (ANOVA) decomposition used in statistics. Another cutHDMR will be shown to be computationally more efficient than the ANOVA decomposition. Application of the HDMR tools can dramatically reduce the computational effort needed in representing the input–output relationships of a physical system. In addition, the hierarchy of identified correlation functions can provide valuable insight into the model structure. The notion of a model in the paper also encompasses input–output relationships developed with laboratory experiments, and the HDMR concepts are equally applicable in this domain. HDMRs can be classified as nonregressive, nonparametric learning networks. Selected applications of the HDMR concept are presented along with a discussion of its general utility.     

Synthesis of β‐Chlorinated Macrocyclic [Au(C14H20N4Cl2)]X (X = AuCl2, ClO4, AuCl4) Gold(III) Complexes. Crystal and Molecular Structures of [Au(C14H20N4Cl2)]ClO4

A squareplanar [AuL₂]⁺ gold(III) complex [L₂ = 6.13dichloro5,7,12,14tetramethyl1,4,8,11tetraaza4,6,11,13tetraenato(2-)] containing two chlorine atoms in the position of the ligand hexacyclic ring was first synthesized by the reaction of the [AuL₁]⁺ tetraiminate complex [L₁ = 5,7,12,14tetramethyl1,4,8,11tetraaza4,6,11,13tetraenato(2-)] with HAuCl₄ in an acetone – DMFA solution. The complex was isolated in the form of dichloroaurite (I), perchlorate (II), and tetrachloroaurate (III). Compounds I–III were studied by elemental and Xray diffraction analyses and IR and NMR spectroscopies. Single crystals of [AuL₂]ClO₄ were obtained, and the crystal structure of this compound was determined from Xray diffraction patterns. The crystals are monoclinic: a = 10.147(2), b = 7.260(1), c = 12.519(2), = 96.70(1)°, V = 915.9(3)³, Z = 2, space group P2/c, d_calc = 2.218, d_meas = 2.209 g/cm³ The crystal structure is built of nearly planar [Au(C₁₄H₂₀N₄Cl₂)]⁺ cations and [ClO₄]^- anions. Introduction of chlorine atoms into the positions of the hexacyclic rings of the tetraazamacrocycle hardly changes the lengths of the delocalized C N and C C bonds.     

Coupling of thermometric titrimetry and constant-current coulometry: Study and applications

Two systems involving the coupling of thermometric and coulometry are presented. In the first assembly, the two electrodes were in the same compartment. Bromocoulometry was used to test the possibilities of this coupling in the sequential titration of a vitamin C+ aspirin mixture about (10^–4 M) and the determination of enthalpy changes. In a second coupling system, the anodic and cathodic compartments were separated by a sintered-glass disc of porosity 3. The conditions for obtaining an electrochemical cell which is also a good calorimeter are discussed. Examples of applications are given, such as analytical measurements, the study of an electrochemically catalysed reaction and of the thermal effects of electrode reactions.

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Zusammenfassung Zwei Systeme werden beschrieben, die eine Kombination von thermometrischer Titrimetrie und Coulometrie darstellen. Bei der ersten Vorrichtung sind die Elektroden im gleichen Raum Untergebracht. Die Bromocoulometric wurde zur Testung der durch diese Kombination für die aufeinanderfolgende Titration von Vitamin C/Aspirin Gemischen (ungefähr 10^–4 M) und für die Bestimmung der Enthalpieänderungen gebotenen Möglichkeiten angewandt. In einem zweiten kombinierten System waren Anoden- und Kathodenraum durch ein Sinterglasfilter der Porosität 3 voneinander getrennt. Es werden die Bedingungen diskutiert, die notwendig sind, um eine elektrochemische Zelle zu erhalten, die zugleich auch ein gutes Kalorimeter ist. Anwendungsbeispiele sind angegeben, wie analytische Messungen und elektrochemische Untersuchungen katalysierter Reaktionen oder thermischer Effekte von Elektrodenreaktionen.

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, . . — 10^–4 M . — N^o3. , . , , .

     

A variational approach to the Dirichlet–Gabor wavelet‐distributed approximating functional

We show that the Dirichlet–Gabor waveletdistributed approximating functional (DAF) can be derived from the same variational principle used to obtain noninterpolating waveletDAFs (such as the Hermite DAF). This variational approach for such interpolating DAFs complements the original viewpoint that they are generated by regularizing interpolating shells or through twoparameter Dirac delta sequences.