The role of the nano-environment of supported gold catalysts in the activity control. Modification of Au/Al2O3 catalysts by redox-type metal oxides

Au/Al₂O₃ catalysts were modified by different redox metal oxides, such as FeO_x, MnO_x and CoO_x, resulting in a pronounced activity increase in CO oxidation.     

Wrong gas/liquid partition data by gas chromatography

In a paper published in 1992 [K.S. Reddy, J.-Cl. Dutoit, E.sz. Kováts, Pair-wise interactions by gas chromatography. I. Interaction free enthalpies of solutes with non-associated primary alcohol groups, J. Chromatogr. 609 (1992) 229] retention indices and standard chemical potential differences (SPOT-s) are given for about 160 solutes on a liquid branched paraffin hydrocarbon of the carbon number, z = 78. For the temperature dependence of the SPOT-s the proposal of Kirchhoff was accepted i.e. that at higher temperatures the molar heat capacity difference of the solute between the gas phase and the solution is nearly constant in a broad temperature range. The data were determined under conditions where the effect of adsorption could be neglected. By comparing the published data with those determined on another branched paraffin of the carbon number, z = 87 [F. Riedo, D. Fritz, G. Tarján, E.sz. Kováts, A tailor-made C87 hydrocarbon as a possible non-polar standard stationary phase for gas chromatography, J. Chromatogr. 126 (1976) 63] it is shown that the reported thermodynamic constants of solutes determined experimentally at higher temperatures (the group "H") are wrong on C78. In the present paper, the method of correction and the resulting corrected data are given. In later papers retention data are given on eight polar derivatives of the hydrocarbon C78 relative to those measured on the nonpolar standard [R. Cloux, G. Défayes, K. Fóti, J.-Cl. Dutoit, E.sz. Kováts, Pair-wise interactions by gas chromatography. III. Synthesis of isosteric stationary phases for gas chromatography, Synthesis (1993) 909; G. Défayes, K.S. Reddy, A. Dallos, E.sz. Kováts, Pair-wise interactions by gas chromatography. V. Interaction free enthalpies of solutes with primary chloro- and bromo-alkanes, J. Chromatogr. A 699 (1995) 131; K.S. Reddy, E.sz. Kováts, Pair-wise interactions by gas chromatography. II. Sociation free enthalpies of some hydrogen bonding solutes with non-associated primary alcohol groups, Chromatographia 34 (1992) 249; K.S. Reddy, R. Cloux, E.sz. Kováts, Pair-wise interactions by gas chromatography. IV. Interaction free enthalpies of solutes with trifluoromethyl-substituted alkanes, J. Chromatogr. A 673 (1994) 181; K.S. Reddy, R. Cloux, E.sz. Kováts, Pair-wise interactions by gas chromatography. VI. Interaction free enthalpies of solutes with primary methoxyalkane, cyanoalkane and alkanethiol groups, J. Chromatogr. A 704 (1995) 387; A. Dallos, A. Sisak, Z. Kulcsár, E.sz. Kováts, Pair-wise interactions by gas chromatography. VII. Interaction free enthalpies of solutes with secondary alcohol groups, J. Chromatogr. A 904 (2000) 211]. Obviously, the same data which are wrong in the nonpolar standard are also wrong in these solvents. The corrected data in the polar solvents are given in supplementary tables.     

Collision-induced dissociation of HS-(HCN): unsymmetrical hydrogen bonding in a proton-bound dimer anion

The energy-resolved competitive collision-induced dissociation of the proton-bound complex [HS.H.CN](-) is studied in a guided ion beam tandem mass spectrometer. H(2)S and HCN have nearly identical gas-phase acidities, and therefore, the HS(-) + HCN and the CN(-) + H(2)S product channels exhibit nearly the same threshold energies, as expected. However, the HS(-) + HCN channel has a cross section up to a factor of 50 larger than CN(-) + H(2)S at higher energies. The cross sections are modeled using RRKM theory and phase space theory. The complex dissociates to HS(-)+ HCN via a loose transition state, and it dissociates to CN(-) + H(2)S via a tight transition state. Theoretical calculations show that the proton-transfer potential energy surface has a single minimum and that the hydrogen bonding in the complex is strongly unsymmetrical, with an ion-molecule complex of the form HS(-)..HCN rather than CN(-)..H(2)S or an intermediate structure. The requirement for proton transfer before dissociation and curvature along the reaction path impedes the CN(-) + H(2)S product channel.     

Novel polycyclic heterocycles. VIII. 6,11-dihydro-12H-dibenzo[b,f] [1,4]thiazocines and their derivatives

6,11-Dihydro-12H-dibenzo[b,f][1,4]thiazocine, 4 , and its 2-chloro, 7 , and 2-(trifluoromethyl)-, 1 , derivatives, were prepared by the reaction of an o-aminobenzenethiol and α,α-dibromo-o-xylene. Acylation and alkylation at position-12 gave a series of ω-haloacyl-, ω-amino-acyl, and ω-aminoalkyl derivatives of these heterocycles. The conformations, proton magnetic resonance spectra, and x-ray crystallographic studies of these compounds are discussed.     

Vertex-Disjoint Cycles Containing Specified Edges

Dirac and Ore-type degree conditions are given for a graph to contain vertex disjoint cycles each of which contains a previously specified edge. One set of conditions is given that imply vertex disjoint cycles of length at most 4, and another set of conditions are given that imply the existence of cycles that span all of the vertices of the graph (i.e. a 2-factor). The conditions are shown to be sharp and give positive answers to conjectures of Enomoto in [3] and Wang in [5]. Revised: July 28, 1999