N. S. Kulikov

Oxidation of Organosulfur Compounds by Hydrogen Peroxide in the Presence of Niobium and Vanadium Peroxo Complexes

New niobium(V) peroxo complexes containing aspargine and Schiff base ligands were synthesized, and their structures were solved by IR, NMR, and mass spectrometric methods. They were found to be catalytically active for the peroxidation of methyl phenyl sulfide and benzothiophene to the corresponding sulfoxide and sulfones. It was shown that vanadium(V) peroxo complexes with the same ligands are less active in the oxidation of methyl phenyl sulfide than the niobium complexes.

Gas chromatography-mass spectrometry of the stereoisomers of perhydroanthracene and perhydrophenanthrene

SummaryA gas chromatographic-mass spectrometric study of a mixture of the stereoisomers of perhydroanthracene (PHA) and perhydrophenanthrene (PHP) has been carried out. Separation was accomplished on capillary columns filled with graphitized thermal carbon black. The stereospecific features of the fragments of PHA and PHP are related, in particular, to the intramolecular repulsion of the H...H pairs of the side rings and evidently arise from the low energy of the ionizing electrons. The effect of this interaction is more clearly shown in the fragmentation of PHP, which is related to the angular disposition of the side rings, and which decreases as the structure of the isomers of the molecules becomes flatter. The predominant fragmentation paths, leading to a reduction in tension, arising from the intramolecular repulsion of the H...H pairs, are different for PHA and PHP. The fragmentation of PHA is characterized by the preferred rupture of the bonds of the side rings, while the fragmentation of PHP proceeds through the rupture of the bonds of the middle ring.

Gas chromatography-mass spectrometry in the study of the adsorption of sulfur-containing amino acids on graphitized thermal carbon black

SummaryGas chromatographic — mass spectrometric study of the trifluoroacetyl-methyl esters of sulfur- and hydroxyl-containing amino acids such as methionine, cysteine, D-β,β′-dimethylcysteine (D-penicillamine), serine, and threonine was carried out. Sterling hydrogen treated graphitized thermal carbon black (HTGTCB) was used as the adsorbent. The Henrys constants, and the initial differential adsorption heats of these amino acid derivatives were determined on the HTGTCB surface by gas chromatography.Introduction of two methyl groups into the β-position of a cysteine molecule (β,β′-dimethylcysteine) stimulates the intramolecular nonvalent interactions increasing the internal rotation barriers in the molecule. This is revealed in the sharply reduced retention of the β,β′-dimethylcysteine derivative on the HTGTCB surface (as compared to the cysteine derivative) and it also influences the fragmentation pathways under electron impact.

Alkylation of schleyer's lithiocarbon C4Li4 by methyl iodide

Abstract Alkylation of lithiocarbon C 4 Li 4 gives the hydrocarbon C 8 H 12 to which the structure of tetramethyltetrahedrane has been ascribed.

Physicochemical and catalytic properties of micro-mesoporous zeolite materials

Micro-mesoporous zeolite materials differing in their content of micro- and mesopores are obtained by the recrystallization of modernite zeolite. Using physicochemical methods such as scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction analysis, small-angle X-ray scattering analysis, low-temperature adsorption of nitrogen, temperature-programmed desorption of NH3, and IR spectroscopy, it is shown that recrystallization leads first to the formation of mesopores with sizes of 20–30 Å in zeolite crystals, then to the appearance of zeolite/MCM-41 nanocomposite, and finally to the complete conversion of zeolite into mesoporous MCM-41. During this process, the concentration of strong Brønsted acid sites accessible to pyridine bases first increases then drops. The catalytic properties of the synthesized materials are studied in the reaction of alkylation of benzene by dodecene-1. It is shown that the creation of transport pores and the increase in the accessibility of acid sites due to recrystallization under soft conditions facilitate the alkylation reaction.

Molecular modelling in chromatostructural analysis : A new approach to the GC/MS study of isomers

The importance of gas-solid chromatography as a source of additional data for the positive structural elucidation of novel isomers by gas chromatography/mass spectrometry is discussed. As an example, a mixture of 11 isomers of perhydroanthracene and perhydrophenanthrene has been considered. The retention parameters of these isomers on thermally graphitized carbon black (TGCB) were calculated by Kiselevs method to predict the order of their separation on a column packed with TGCB. The molecular models required for these calculations were constructed using a conventional approach and molecular mechanics; the corresponding results obtained are compared. The order of separation predicted by molecular mechanics appeared close to that observed experimentally.

Relation between the structure of molecules of nitrogen-containing heterocyclic compounds and their adsorption on graphitized carbon black

The retention volumes for small (zero) sample size (Henry constants) of hydrogen-treated graphitized thermal carbon black (HTGTCB) in five- or six-membered mono- and bicyclic nitrogen-containing compounds have been determined. Comparison of Henry constants K1 and initial heats of adsorption q̄1 of nitrogen-containing heterocyclic compounds with those of hydrocarbons of a similar structure has shown that adsorption of the studied heterocyclic compounds on HTGTCB depends on the number and position of nitrogen atoms in their molecules. An increase in the number of nitrogen atoms in flat molecules of azoles (pyrrole, pyrazole, 1,2,4-triazole) brings about the growth of K1 and q̄1. In six-membered cycles the growth of K1 and q̄1 is observed only during the transition from pyridine to 1,2-diazine (pyridazine), whereas in transition to 1,3- and 1,4-diazines (pyrimidine and pyrazine), and further on to s-triazine, the retention greatly reduces. In azanaphthalenes (quinoline, cinnoline, quinoxaline) and benzazoles (indole, indazole) the growing number of nitrogen atoms also results in weaker retention.

Nucleophilic substitution in dibenz[b,d]iodolium and 11,12-dihydro-10H-dibenz[b,g]iodocinium cations

Treatment of dibenz[b,d]iodolium tetrafluoroborate with NO2−, Br−, and N3− ions gave, along with nucleophilic substitution products, 2-nitro-, 2-bromo-, and 2-azido-2′-iodiphenyls, diphenyl, 2-iododiphenyl, and 2,2′-diiododiphenyl (products of one electron reduction), whereas 11,12-dihydro-10H-dibenz[b,g]iodocinium tetrafluoroborate underwent nucleophilic substitution with all three nucleophiles to give a single product in each case: 1-(2-nitrophenyl)-, 1-(2-bromophenyl)-, or 1-(2-azidophenyl)-3-(2-iodophenyl)propane.

Mass spectrometry and structure of heterocyclic ions by collisional activation.

The fragmentation of isomeric dimethylnitroindolizines due to electron impact was studied by collisional activation and high resolution mass spectroscopy. The [M-OH]+ ion which is formed as a result of the ortho-effect was found to have a variable structure. In the case of 2,8-dimethyl-1-nitroindolizine, one of the main fragmentation processes of [M-OH]+ is the elimination of an H2O molecule.

Tetracyanoethylation and Fischer rearrangement of some 4-oxo-4,5,6,7-tetrahydroindoles

The reaction of the 1,2-diaryl-4-oxo-4,5,6,7-tetrahydroindoles, and 3-methyl-4-oxo-4,5,6,7-tetrahydroindole with tetracyanoethylene occurred at the 5 position of the tetrahydroindole ring. A Fischer rearrangement of the phenylhydrazones of these 4-oxotetrahydroindoles gave pyrrolo [2,3-c]carbazoles.