Dielectric properties of ethyleneglycol-1,4-dioxane mixtures using TDR method

Complex permittivity has been determined for mixtures of ethyleneglycol-1,4-dioxane (EG-DX) with various concentrations in the frequency range from 100 MHz to 30 GHz at 25 degrees C by time domain reflectometry (TDR). A primary process with an asymmetric shape and a Debye-type small-amplitude high-frequency process are observed for each mixture. The deviation of the relaxation time for the primary process from that of the ideal mixture shows a maximum value at a mole fraction of 1,4-dioxane, xDX approximately =0.8. The static permittivity for the mixtures can be explained using the Luzar model by assuming the formation of two types of hydrogen-bonded dimers, one between EG-EG (pair 1) and the other between EG-DX (pair 2). The number of these pairs is also estimated as a function of concentration. These results of the relaxation time and static permittivity are interpreted on the basis of a model of two kinds of cooperative domains coexisting in the mixtures.     

Synthesis,Characterization, Catalytic and Antibacterial Activity of Two Series of Dinuclear Ruthenium Sulphoxide Complexes Using 5,5¢‐Methylenebis(pyridine) as Bis‐chelating Bridging Ligand

The reaction of a new heterocyclic bidentate N containing spacer, (ligand) 5,5′‐methylenebis(pyridine) with ruthenium sulphoxide precursors resulted, dinuclear complexes. We herein report three formulations; [{cis,fac‐RuCl₂(so)₃}₂(μ‐mbp)].3so; [{trans,mer‐RuCl₂(so)₃₂}₂(μ‐mbp)].3so and [{trans‐RuCl₄(so)}₂(μ‐mbp)]^2?[X]₂⁺; where so = dimethyl‐sulfoxide/tetramethylenesulfoxide; mbp = 5,5′‐methylenebis(pyridine) and [X]⁺ = [(dmso)₂H]⁺, Na⁺ or [(tmso)H]⁺. These complexes were characterized on the basis of elemental analyses, molar conductance measurement, magnetic susceptibility, FT‐IR, ¹H‐NMR, ¹³C{¹H}‐NMR, electronic spectroscopy and FAB‐Mass spectrometry. Catalytic activity of these complexes has been investigated in hydrolysis of benzonitrile. All the complexes exhibit good antibacterial activity against gram‐negative bacteria Escherichia coli in comparison to Chloramphenicol.     

Dielectric studies of alkyl acrylates with primary alcohols using time domain reflectometry

Binary polar–polar liquid mixtures of alkyl acrylates (methyl acrylate, ethyl acrylate and butyl acrylate) with primary alcohols (propan-1-ol, butan-1-ol and hexan-1-ol) were subjected to dielectric studies at 303?K for different concentrations using time domain reflectometry (TDR) over the frequency range from 10?MHz to 10?GHz. Static permittivity (ε₀) dielectric constant at high frequency (ε_∞) and relaxation time (τ) were found through dielectric measurements for different concentrations of each system. The Bruggeman dielectric factor, Kirkwood correlation factor and the excess inverse relaxation time were determined and discussed to yield information on the molecular interactions of the systems. Deviations from the linearity of various models suggest molecular association through hydrogen bonding between the ?OH group of alcohols and C=O group of esters. The results also show a dependence of dielectric parameters on the alkyl chain length of both the alcohols and esters.     

An empirical evaluation of walk-and-round heuristics for mixed integer linear programs

Feasibility pump is a general purpose technique for finding feasible solutions of mixed integer programs. In this paper we report our computational experience on using geometric random walks and a random ray approach to provide good points for the feasibility pump. Computational results on MIPLIB2003 and COR@L test libraries show that the walk-and-round approach improves the upper bounds of a large number of test problems when compared to running the feasibility pump either at the optimal solution or the analytic center of the continuous relaxation. In our experiments the hit-and-run walk (a specific type of random walk strategy) started from near the analytic center is generally better than other random search approaches, when short walks are used. The performance may be improved by expanding the feasible region before walking. Although the upper bound produced in the geometric random walk approach are generally inferior than the best available upper bounds for the test problems, we managed to prove optimality of three test problems which were considered unsolved in the COR@L benchmark library (though the COR@L bounds available to us seem to be out of date).     

Alpha radioactivity for proton-rich even Pb isotopes

Half-lives for alpha radioactivity from proton-rich even Pb isotopes in the range A = 182–202 have been calculated using the unified fission-like approach. The geometrical shape of the potential barrier is parametrized in terms of a highly versatile, asymmetric and analytically solvable form of potential based on Ginnochio’s potential. Good agreement with the experimental data has been obtained with the variation of just one parameter. Half-lives of three unknown alpha emitters in the neutron-deficient Pb chain (¹⁹⁸Pb, ²⁰⁰Pb and ²⁰⁴Pb) have been predicted. The exact expression for the transmission coefficient has been compared with those obtained from WKB approximation method for symmetric Eckart potential.      

Aluminum five‐ and six‐coordination in bis(acetylacetonato)aminoalkoxides

Reactions of bis(acetylacetonato)aluminum(III)‐di‐μ‐isopropoxo‐di‐isopropoxo aluminum(III), [(CH₃COCHCOCH₃)₂Al(μ‐OPrⁱ)₂Al(OPrⁱ)₂] with aminoalcohols, (HO R NR¹R²) in 1:1 and 1:2 molar ratios in refluxing anhydrous benzene yielded binuclear complexes of the types [(CH₃COCHCOCH₃)₂Al(μ‐OPrⁱ)₂Al(O R NR¹R²)(OPrⁱ)] and [(CH₃COCHCOCH₃)₂Al(μ‐OPrⁱ)₂Al(O R NR¹R²)₂] (R   (CH₂)₃ , R¹ = R² = H; R =  CH₂C(CH₃)₂ , R¹ = R² = H; R =  (CH₂)₂ , R¹ = H, R² =  CH₃; and R   (CH₂)₂ , R¹ = R² = CH₃), respectively. All these compounds are soluble in common organic solvents and exhibit sharp melting points. Molecular weight determinations reveal their binuclear nature in refluxing benzene. Plausible structures have been proposed on the basis of elemental analysis, molecular weight measurements, IR, NMR (¹H, ¹³C, and ²⁷Al), and FAB mass spectral studies. ²⁷Al NMR spectra show the presence of both five‐ and six‐coordinated aluminum sites. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:518–522, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10184     

Pyrolysis of Nickel Zirconyl Oxalate

Nickel zirconyl oxalate hexahydrate (NiZrOx) is δ prepared and characterised by I.R. spectral and chemical analysis. Its thermal decomposition has been investigated by employing TG, DTG, DTA and chemical analysis. End product was identified by X-ray diffraction studies. The decomposition proceeds through four steps i) dehydration of NiZrOx in two steps, ii) partial decomposition of oxalate to give an oxalate carbonate intermediate, iii) decomposition of oxalate to give a non-stoichiometric carbonate and iv) decomposition of this non-stoichiometric carbonate to give the end product a mixture of NiO+ZrO₂. On the basis of the results obtained, a tentative scheme for the decomposition of NiZrOx is proposed.     

Dihydroboration of cyclic allenes

The study on the dihydroboration of a large ring cyclic allene, 1,2-cyclotridecadiene and the smallest stable allene, 1,2-cyclononadiene is described. For example, a mixture of products containing isomeric cyclotridecene, bicyclo(10.1.0)-tridecane, cyclotridecanone, cyclotridecanol, isomeric cyclic 1,2-cyclotridecandiol and isomeric 1,3-cyclotridecandiol is obtained from dihydroboration-oxidation of 1,2-cyclotridecadiene. However, dihydroboration-hydrolysis-oxidation of 1,2-cyclotridecadiene affords mainly cyclotridecanol, whereas dihydroboration-oxidation with chromium trioxide-pyridine yields mainly a mixture of Z- and E-cyclotridecene. Reasonable mechanistic pathways have been suggested for the formation of products. The proposed unusual elimination reaction of 1,2-diorganoboranes with chromium trioxide has been substantiated using an authentic 1,2-diorganoborane from diphenyl acetylene. The reaction appears to be stereospecific withthreo-diorganoborane furnishing predominantly E-alkene. The results with 1,2-cyclononadiene has also been rationalised on a similar basis.     

Thermal decomposition of barium oxomolybdenum(VI) oxalate

A new molybdenum(VI) oxalato complex, Ba[MoO₃(C₂O₄)]·3H₂O (BMO), was prepared and characterized by chemical analysis and infrared spectral studies. Thermal decomposition studies were made using thermogravimetry and differential thermal analysis. Dehydration reactions take place up to 280°C in three stages with loss of one half, one and a half and one mole of water per mole of BMO, respectively. Decomposition of oxalate takes place between 280 and 435°C in a single step to give BaMoO₄ as the end product, which was characterized by chemical analysis, infrared and X-ray studies. The X-ray diffraction pattern of BMO shows that it is an amorphous compound. A chain structure containing MoO₆ octahedra linked through oxygen is proposed on the basis of the infrared absorption spectrum.     

Lanthanons(III) Complexes of Bifunctional Tridentate Schiff's Bases

A systematic study of the reactions of isopropoxides of praseodymium, neodymium and samarium with bifunctional tridentate Schiff bases (acetylacetone-O-aminophenol and benzoylacetone-O-aminophenol) in equimolar ratios resulting in the formation of products with formula M(OPrⁱ) (SB), M(SB) (SBH) and M₂(SB)3 (where SB is Schiff base anion, SBH is Schiff base and M is metal). The reactions have been found to be quite facile even at the room temperature as observed by immediate change of colour. The intensity of the colour of acetylacetone-O-aminophenol derivatives of rare earths decreased with the increasing stoichiometric ratio of the ligand i.e. from yellow to light yellow.