Randić index and lexicographic order

Let T be a tree and consider the Randi index (T)= ), where v _i –v _j runs over all edges of T and (v _i ) denotes the degree of the vertex v _i . Using counting arguments we show that the Randi index, is monotone increasing over the well (lexicographic order) ordered sequence of trees with unique branched vertex.     

Modification of the catalyst surface in 1,2-dichloroethane decomposition

The strong and irreversible chemisorption of substrate or (and) reaction products (self-poisoning of catalyst surface) has been found to account for an activity decrease and changes in catalytic selectivity in the reaction. The mechanism of 1,2-dichloroethane (1,2-DCE) decomposition has been discussed.

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1,2- (1,2-), , . , — — () («» ) . 1,2-.

     

On the Distribution of π-Electrons into Rings of Conjugated Hydrocarbons Containing a Linear Polyacene Fragment

A method for assessing the -electron contents (EC) of rings of benzenoid hydrocarbons, based on the examination of their Kekulé structures, was recently put forward by Balaban and Randi. We now show that all hexagons belonging to a linear polyacene fragment of a conjugated hydrocarbon (not necessarily benzenoid) have mutually equal EC-values.     

Characterization of distribution of pi-electrons amongst benzenoid rings for Randić’s “algebraic” Kekulé structures

For benzenoid hydrocarbons the distribution of pi-electrons amongst rings is characterized in the context of Randis mode of assignment attending to the different Kekulé structures. In particular the mean and mean deviation from the mean are considered, and the benzenoids which achieve maximum deviation are identified.     

Studies of the effect of strong metal-support interaction (SMSI) over model catalyst Rh/TiO2

The effect of strong metal-support interaction (SMSI) has been studied over Rh/TiO₂ as a model catalyst. Adsorbability variations during SMSI state generation have been found to be due to the production of Rh–Ti alloy. - Rh/TiO₂. , SMSI Rh–Ti.     

Kinetics and mechanism of the ligand substitution reaction of aquodiethylenetriaminepentaacetatoruthenate (III) in aqueous solution

The kinetics of ligand substitution reactions of [Ru(H₂dtpa) (H₂O)] (2) (H₂dtpa=diprotonated diethylenetriaminepentaacetic acid) were studied as a function of ligand (L) concentration, pH (2.5–8.0) and temperature (30–45 °C) at 0.2 M ionic strength. The equilibrium constants for the formation of mixed ligand complex [Ru^III(dtpa) (L)] (L=2-mercaptopyrimidine, cysteine) and the distribution of various species in solution in the pH range of 2.5–8.0 were computed from potentiometric results. [Ru(H₂dtpa) (H₂O)] ( H₂dtpa= ) , pH (2,5–8,0) (30–45°C) 0,2 M. [Ru^III(dtpa) (L)] ( L=2-, ) pH=2,5–8,0.     

Kinetic studies of methylmercaptan production from dimethyl sulfide and H2S

Kinetic regularities of methylmercaptan production from dimethyl sulfide and H₂S in the presence of -Al₂O₃ have been studied under gradientless conditions. A stepwise reaction mechanism is suggested implying that the catalyst surface is methoxylated by methyl sulfide and then CH₃O groups interact with H₂S. The kinetic equation obtained describes fairly well this process on the nonhomogeneous catalyst surface. H₂S -Al₂O₃. , , CH₃O- H₂S. , .     

Phase equilibrium diagram for the tin(II) iodide-copper(I) iodide system

The phase diagram of the SnI₂-CuI system was determined by the method of thermal analysis. No intermediates were found. It is suggested that limiting solid solutions of SnI₂ in-CuI,-CuI and-CuI, respectively, are formed. The eutectic point parameters (32.7 mol% CuI, 270.4 ±0.1 °C) and those of two invariant points (64.0 mol% CuI, 385.3 ±0.5 °C and 61.5 mol% CuI, 366.6±0.2 °C), corresponding to the equilibria+liquid and+liquid , respectively, were determined.Mittels Thermoanalyse wurde das Phasendiagramm SnI₂-CuI bestimmt. Es konnten keine Intermediäre gefunden werden. Es scheint, daß Grenzmischkristalle von Shl2 und-CuI,-CuI,-CuI gebildet werden. Es wurden ein Eutektikum (32,7 mol% CuI, 270,4 ± 0,1 °C) und zwei den Gleichgewichten+Flüssigkeit und+Flüssigkeit entsprechende invariante Punkte (64,0 mol% CuI, 385,3±0,5 °C und 61,5 mol% CuI, 366,6±0,2 °C) gefunden. SnI₂-CuI, . , , -CuI,-CuI Cul. (32,7 % CuI, 270,4±0,1°) (64,0 % Cul, 385,3 ±0,5° 61,5 % CuI, 366,6±0,2°), + + .

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The present work was carried out within the framework of contract CPBP 01.15.     

Transformation of batridene

Transformations of 1,1,6,6,7,7-hexahydroxy-3,3-dimethyl-5,5-diisopropyl-2,2-dinaphthylidene-8,8-dibarbituric acid (batridene) in DMSO are studied.     

On the Distribution of π-Electrons into Rings of Conjugated Hydrocarbons Containing a Linear Polyacene Fragment

Summary. A method for assessing the -electron contents (EC) of rings of benzenoid hydrocarbons, based on the examination of their Kekulé structures, was recently put forward by Balaban and Randi. We now show that all hexagons belonging to a linear polyacene fragment of a conjugated hydrocarbon (not necessarily benzenoid) have mutually equal EC-values.     

Chemisorptive characterization of Mn2+ cation effects on fused iron-catalysts

Volumetric and pulse chemisorptions of carbon monoxide (CO) have been developed to characterize effects of Mn²⁺ cations on an industrial doubly promoted fused iron catalyst. Addition of Mn²⁺ cations induces an increase in Fe dispersity, Fe electronic density and stability of the Mn²⁺-containing iron catalyst, where the same increase is observed by XPS and SEM. These effects explain why the activity of Mn²⁺-containing iron catalysts is improved. Mn²⁺ , . Mn²⁺ Fe, Fe , XPS SEM. . Mn²⁺ .     

Jovanović adsorption isotherm for gaseous mixtures

A derivation of theJavanovi isotherm for mono and multilayer adsorption of gaseous mixtures was obtained.

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Jovanovi-Adsorptions-Isotherme für Gasmischungen (Kurze Mitteilung)

Zusammenfassung Es wird die Ableitung derJovanovi-Adsorptionsisotherme für mono- und multimolekulare Adsorption angegeben.

     

Abnormally high fractal dimension of silica surfaces measured by adsorption of aliphatic alcohols

Factors leading to abnormally high fractal dimension D of silica surfaces measured by adsorption of aliphatic alcohols have been analyzed. , D .     

Studies of the interaction of 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) with imidazole in acetonitrile

The reaction of DDQ with imidazole in acetonitrile is a two-step process. The formation of an anion radical is followed by slow substitution of Cl atoms to form diaminobenzoquinone. Kinetics of the second step is reported. . - Cl CN- . .     

Alkylation of p-substituted phenols by heteropoly acids

Liquid-phase alkylation of p-tert-butylphenol (TBP) and p-cresol by olefins and benzyl chloride in the presence of solid heteropoly acids (HPA) H₃PW₁₂O₄₀ and 25% H₃PW₁₂O₄₀/SiO₂ at 100–150°C provides high yields of mono- and disubstituted products. HPAs are more active than H₂SO₄, easily separated from the reaction mixture and can be used repeatedly. -- () - () H₃PW₁₂O₄₀ 25% H₃PW₁₂O₄₀/SiO₂ 100–150°C - - . , H₂SO₄, - - .     

Ab Initio Study of Prednisolone, 6α-Fluoroprednisolone, 9α-Fluoroprednisolone,and 6α,9α-Difluoroprednisolone

A theoretical study of prednisolone, 6-fluoroprednisolone, 9-fluoroprednisolone, and 6,9-difluoroprednisolone has been performed at the ab initio HF/6-31G, MP2/6-31G, and B3LYP/6-31G levels. Structural information and the electronic features of prednisolone and its derivatives and the synergistic effect of 6,9-difluoroprednisolone was examined. Contrary to the AM1 and MNDO results, we found 9-fluoroprednisolone is more stable than the 6-fluoroprednisolone. The increased corticosteroid activity of the 6,9-difluoroprednisolone is most likely due to electronic effects, mainly related to the receptor binding.     

Baseline interpolation in DTA and DSC quantitative analysis of slow processes

A simple method is described for use with the differential scanning calorimeter for baseline interpolation in continual processes over a wide temperature interval. For the process of water desorption from the synthetic zeolite LiA with the coveragegq=1.5, the measured heat of desorption wasQ=11.2±0.5 kcal/mole.The authors wish to thank V. Vueli and D. Karauli for their help and interest in solving the problem of the baseline interpolation.     

Salt effects in the reaction between IrCl62? and MnEDTA2?

The oxidation of MnEDTA^2–. (EDTA=ethylenediaminetetra-acetate) by hexachloroiridate(IV) has been studied in concentrated electrolyte solutions at 298 K. The estimation of the activity coefficients of the species from the Stokes-Robinson hydration theory indicates that the observed salt effects have their origin in a greater destabilization of the initial state with respect to the transition state when increasing salt concentration. MnEDTA^2– (EDTA= ) (IV) . -, , .