Effect of Water Vapor on Chromatographic Characteristics of the Cyclodextrin-Containing Stationary Liquid Phase in Capillary Gas Chromatography

The effects of the presence of water vapor in the carrier gas and the temperature on the retention of achiral and chiral compounds, enantioselectivity, and performance of an open-tubular column with a cyclodextrin-containing phase were studied. The use of a carrier gas containing water vapor in the determination of optically active isomers, such as camphor, slightly increases the retention factor. A substantial improvement of performance characteristics of the column was found: for hydroxy compounds, the column performance increased by two to three times and the peak symmetry improved by more than twice.     

Voltammetric studies of the Kolbe synthesis with perfluorocarboxylic acids prepared from hexafluoropropene oxide oligomers

Carboxylic acids prepared from hexafluoropropene oxide CF₃CF₂CF₂O[CF(CF₃)CF₂O]_nCF (CF₃)COOH [n = 0, 2,5-bis(trifluoromethyl)-3,6-dioxaperfluorononanoic acid; n = 1, 2,5,8- tris(trifluoromethyl)-3,6,9-trioxaperfluorododecanoic acid], according to voltammetric data, enter the Kolbe reaction both at the Pt anode and at anodes from carbon materials in H₂O-CH₃CN and CH₃OH-CH₃CN solutions. The critical potential appreciably depends both on the anode material and on the solvent composition. Favorable effect of pyridine additions in H₂O-CH₃CN solutions is due to replacement of water molecules from the electrical double layer. The sodium ions exert a negative effect on the Kolbe synthesis.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 11, 2004, pp. 1842–1846.Original Russian Text Copyright © 2004 by Chechina, Sokolov, Tomilov.This revised version was published online in April 2005 with a corrected cover date.     

Fullerenes as a new type of ligands for transition metals

Fullerenes are considered as ligands in transition metal π-complexes. The following aspects are discussed: metals able to form complexes with fullerenes; haptic numbers; homo-and heteroligand complexes; ligand compatibility with fullerenes for different metals, including fullerenes with a disturbed structure of conjugation.     

Fluorinated triazinones from hexafluoroacetone ethoxycarbonylimine

The behavior of hexafluoroacetone ethoxycarbonylimine in cyclocondensation with different binucleophiles of the amidine type, viz., amino derivatives of N- and N,S-heterocycles, was studied. A preparative method for the synthesis of previously unknown annelated 2,2-bis(trifluoromethyl)-1,3,5-triazinones was developed.     

Influence of pore diffusion on the rate of n-heptane conversion on a Pt/Al2O3 catalyst under reforming conditions

Under reforming conditions, the rate of n-heptane conversion on a large Pt/Al₂O₃ catalyst grain, in contrast to that in the kinetic region, depends on the hydrogen to hydrocarbon mole ratio. The rate equation for the reaction on a large grain agrees well with the experimental results obtained by a gradientless method under pressure.

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Crystal Structures of Two Re(V) Complexes of 3,5-Dimethylpyrazole with Linear and Bent [OReOReO]4+ Fragments

The crystal structures of two new dimer compounds of Re(V) containing an [OReOReO]⁴⁺ fragment have been studied. Re₂O₃Cl₄(3,5-Me₂pzH)₄ (I): space group P2¹/n, Z = 4, a = 10.180(3), b = 18.132(3), c = 16.601(2) , = 94.60(2)°, V = 3054.4(1) ³, d _calc = 2.059 g/cm³, R ₁ = 0.0513, wR₂ = 0.1493 for 4701 I_hkl > 2 _I of 4926 measured reflections; Re₂O₃Cl₂(-3,5-Me₂pz)₂(3,5-Me₂pzH)₂2[(3,5-Me₂pzH₂)Cl] (II): space group P2₁/n, Z = 4, a = 16.904(2), b = 14.573(1), c = 17.401(2) , = 107.23(1)°, V = 4094.2(7) ³, d _calc = 1.848 g/cm³, R ₁ = 0.025, wR₂ = 0.0514 for 6102 I_hkl > 2 _I of 6315 measured reflections (Enraf-Nonius CAD-4 diffractometer, MoK, graphite monochromator). Compound I has a molecular structure, where molecules are dimers Re₂O₃Cl₄(3,5-Me₂pzH)₄ with a bridging O atom. In II, the dominant motif is the ReOCl(3,5-Me₂pzH) fragments bridged by the pyrazole molecules and the O atom.     

Potential function of internal rotation of (CH3)2CClNO,CH3CCl2NO,and their deuterium analogs

The potential function has been constructed for internal rotation of the NO-group in (CH₃)₂CClNO, CH₃CCl₂NO, and their deuterium analogs. It has been established that the N=O bond in the cis_Cl conformer of CH₃CCl₂NO does not eclipse the C-Cl bond, rather forming an angle of approximately 30. It has been shown that a change in substitutent on the -carbon atom may produce a substantial change in the form of the potential function of internal rotation (PFIR) of the NO group.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 550–555, March, 1990.