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.     

Solubility enhancement of triflumizole by host-guest interaction with β-cyclodextrin

Summary The solubility enhancement of triflumizole, a systemic fungicide, by -cyclodextrin inclusion complexation was investigated by electron absorption spectroscopy. The respective association constant determined by different methods was estimated to 470±20M ^–1 in aqueous solution. A model for the host-guest complexation was deduced by molecular calculations.

---

Löslichkeitsverbesserung von Triflumizole durchHost-Guest-Complexierung mit -Cyclodextrin

Zusammenfassung Die Löslichkeitsverbesserung des systemischen Fungizids Triflumizole durch Komplexierung mit -Cyclodextrin wurde mittels Elektronenabsorptionsspektroskopie untersucht. Die entsprechende Stabilitätskonstante wurde durch verschiedene Methoden erfaßt und betrug im wäßrigen Medium 470±20M ^–1. Ein Model für denHost-Guest-Complex wurde durch Molekülrechnungen erstellt.

     

Asymmetric michael addition of aromatic thiols to 2-cyclohexenone and maleic acid esters via formation of crystalline cyclodextrin complexes

The asymmetric Michael addition of aromatic thiols to 2-cyclohexenone and maleic acid esters has been carried out by utilizing their crystalline cyclodextrin complexes suspended in water. The best chiral induction, 30% enantiomeric excess (ee), was achieved in combinations of 2-cyclohexenone and octyl maleate with the crystalline -cyclodextrin complex of benzenethiol (method A) to afford (S)-3-phenylthiocyclohexanone and (S)-octyl-2-phenylthiosuccinate, respectively, whereas the reaction of benzenethiol with 2-cyclohexenone included in -cyclodextrin (method B) inversely induced the chiral recognition to give the (R)-adduct with 4–9% ee.     

π‐Facial Selectivity in the Formation of Tricarbonylchromium(0) Complexes of Estra‐1, 3, 5(10), 6‐tetraenes

The preparation of two η⁶‐estra‐1, 3, 5(10), 6‐tetraene tricarbonylchromium complexes 4 and 6 are described. In both cases only one stereoisomer can be isolated, in contrast to other estrane‐tricarbonylchromium complexes, where complexations are non‐stereoselective. X‐ray crystal structural analysis of 4 discloses that only the more sterically hindered β‐facial isomer is formed. It is assumed that the 6, 7‐olefinic moiety exerts a directive influence on the complexation.     

Formation of 2,2-difluoro-3-hydroxymethylbenzo-1,4-oxathianes from 2-(α-trifluoromethylvinylthio)phenols)

It is shown that 2,2-difluoro-3-hydroxymethylbenzo-1,4-oxathianes are formed together with 3-trifluoromethylbenzo-1,4-oxathianes whenortho-(-trifluoromethyl--chloroethylthio)phenols are boiled with excess aqueous alkali. The mechanism of the reaction is discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1457–1459, August, 1994.     

Physicochemical properties of π-π complexes of zinctetraphenylporphyrin with aromatic molecules

Features of the solvation of zinctetraphenylporphyrin (ZnTPP) in benzene, toluene,ortho-, meta-, andpara-xylenes were studied by a thermogravimetric method. The temperature ranges of the stability and the compositions of the corresponding specific - complexes were determined from the results of the thermogravimetric investigation of the crystallosolvates of the metalloporphyrin with the solvent molecules, and the energy characteristics of the intermolecular metalloporphyrin—solvent interactions were calculated.Institute of the Chemistry of Nonaqueous Solutions, Russian Academy of Sciences, 153018 Ivanovo. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 7, pp. 1545–1548, July, 1992.     

Reaction paths of some open-shell reactive intermediates

The intermolecular interaction energy for reacting systems in singlet, triplet and doublet states was partitioned by the perturbation expansion method into the chemically meaningful five interaction terms: the Coulomb, exchange-repulsion, induction, dispersion, and charge-transfer energies. In the local ZDO approximation, these energy terms were evaluated for the dimerization of methylenes (^1,3CH₂), the additions of carbenes (^1,3CH₂ and^1,3CF₂) as well as amino radicals (²NH₂ and²NF₂) toward ethylene, and the hydrogen abstractions by methylenes (^1,3CH₂), nitrene (³NH), and hydroxyl radical (²OH) from methane. It has been found that the reaction path is much influenced by the spinmultiplicity, and that the charge-transfer and exchange-repulsion terms play a dominant role in determining the course of reactions.     

Comparison of the Hartree-Fock,Møller-Plesset,and Hartree-Fock-Slater method with respect to electrostatic properties of small molecules

Summary The results of various quantum chemical calculations, the Hartree-Fock (HF) method, the Møller-Plesset perturbation theory (MP2), and the Hartree-Fock-Slater (HFS) method are compared. Atomic charges, dipole moments, topological properties of the electron density distribution and polarizabilities, and first hyperpolarizabilities are calculated. Atomic charges obtained with the HFS method are found to be very close to those calculated with the MP2 method, from which we conclude that the HFS method describes to some extent electron correlation effects. Performing an MP2 calculation after an HF calculation improves the molecular dipole moments considerably, yielding values close to the experimental ones. HFS calculations are computationally less demanding than MP2 and yield comparable results for the electron density distributions, dipole moments and polarizabilities.     

Effects of medium and chemical modification on thermal characteristics of Β-lactoglobulin

The thermal properties of -lactoglobulin (-LG) were studied by differential scanning calorimetry (DSC) under different medium conditions.pH, neutral salts, protein perturbants, and polyols all affected the DSC characteristics of -LG. Acylation with fatty acids also changed the thermal properties, particularly peak width at half-height. The results suggest that the structural stability of -LG is controlled by non-covalent forces, particularly electrostatic and hydrophobic interactions. Disulfide bonds did not contribute to the thermal response of -LG. Fatty N-acyl-amino acids caused marked increases in thermal stability and decreases in denaturation enthalpy, and additional peaks were observed in the presence of some palmitoyl derivatives.Contribution No. 2310, Centre for Food and Animal Research.We thank D. Raymond for her excellent technical assistance.