Analysis of vibratinal spectra of 8-hydroxyquinoline and its 5,7-dichloro, 5,7-dibromo, 5,7-diiodo and 5,7-dinitro derivatives based on density functional theory calculations

The geometry, frequency and intensity of the vibrational bands of 8-hydroxyquinoline and its 5,7-dichloro, 5,7-dibromo, 5,7-diiodo and 5,7-dinitro derivatives were obtained by the density functional theory (DFT) calculations with Becke3-Lee-Parr (B3LYP) functional and 6-31G* basis set. The effects of chloride, bromide, iodide and nitro substituent on the vibrational frequencies of 8-hydroxyquinoline have been investigated. The assignments have been proposed with aid of the results of normal coordinate analysis. The observed and calculated spectra are found to be in good agreement.      

An analysis of SCF and geometry convergence for diatomic molecules

A geometry and SCF convergence study of Hartree-Fock calculations using the 6-31G* basis set is carried out on the set of all possible diatomic molecules formed from atoms with Z≤36. The utility of Hartree-Fock calculations using the smaller STO-3G basis set to improve the convergence behavior is demonstrated.      

Solid-state linear polarized IR-spectroscopy of croconic and rhodizonic acids

The applications of linear-polarized IR-spectroscopy to oriented colloid suspensions in a nematic host are demonstrated with croconic and rhodizonic acids. The experimental IR vibrational assignments of the solid-state of both neutral compounds are presented. Assignments are supported by theoretical quantum chemical calculations and vibrational analysis at the DFT level of theoretical approximation with the 6-311++G^** basis set.      

Spectral study of coumarin-3-carboxylic acid interaction with human and bovine serum albumins

Fluorescence spectroscopy and circular dichroism (CD) spectroscopy were used to investigate the interaction of coumarin-3-carboxylic acid with human serum albumin (HSA) and bovine serum albumin (BSA) under physiological conditions in a buffer solution of pH 7.4.      

Recent development in capillary ion chromatography technology

This review summarizes the development of capillary ion chromatography (CIC) over approximately the last 5 years. It mainly focuses on the technologic aspects of several key components associated with CIC, including micropump, microscale electrodialytic eluent generator, microscale suppressor and the detector.      

Poly(ethyl cyanoacrylate) colloidal particles tagged with Rhodamine 6G: preparation and physicochemical characterization

This paper describes the preparation and characterization of poly(ethyl cyanoacrylate) colloidal particles loaded with the organic fluorophore Rhodamine 6G. We studied the physicochemical properties of the colloidal particles: morphology, size-distribution, ζ-potential, fluorescent properties and photobleaching upon UV-light illumination. The properties of the obtained colloidal particles, as well as the dye loading efficiency, were found to depend on the concentrations of ethyl cyanoacrylate monomer and Rhodamine 6G in the polymerization medium. The fluorophore release from the colloidal particles in aqueous buffer is also studied.      

Nanoporous carbon — metal composites for hydrogen storage

Metal-carbon composites have shown considerable hydrogen storage potential at room temperature. In the present work the behaviour of two different Pd amalgam doped carbon substrates, namely a carbogenic foam and a mildly oxidised ordered mesoporous carbon, are compared on the basis of their hydrogen sorption properties at 77 and 298 K and low pressures, aiming to investigate the effect of surface on the storage capacity. In both cases, the introduction of alloy nanoparticles leads to an improvement of the hydrogen uptake with respect to pure carbons. This effect is significant for the carbogenic foam however small for the ordered carbon.      

Adduct formed by chromium trioxide and zwitterionic quinolinic acid

Chromium trioxide forms an adduct with zwitterionic quinolinic acid. The structure of the product was found to be (quinolinium-3-carboxylato-O)trioxidochromium(VI), determined by single-crystal X-ray diffraction methods. To evaluate the bonding properties of the compound, its structure was optimized at the B3LYP/6-311G* level of theory. The electronic characteristics were investigated by topological methods applied to the total charge density in various model compounds including the title compound, title compound with a HF molecule presenting a hydrogen bonding and anionic moiety. Calculated aromaticity indices indicate that the quinolinic rings tend to conserve their degree of aromaticity against hydrogen bonding. However, when there is hydrogen bonding involving an N-H bond or when the quinolinium zwitterion is deprotonated, there are clear changes in the interaction between chromium trioxide and the quinolinic moiety.      

Metathesis transformations of unsaturated derivatives of β-diketones

Selected β-diketones bearing unsaturated derivatives have been demonstrated to undergo homo-metathesis and cross-metathesis with selected olefins in the presence of Grubbs catalysts. The reactions led to respective homo- and cross-metathesis products mainly with good yields and selectivities.      

Facile dehalogenation of halogenated anilines and their derivatives using Al-Ni alloy in alkaline aqueous solution

This article describes the simple hydrodehalogenation of halogenated anilines and their derivatives by the action of Raney aluminium-nickel alloy in aqueous alkaline solution at room temperature. The reaction course was monitored by means of 1H nuclear magnetic resonance (NMR) spectroscopy and GC-MS spectra.      

Mathematical approach to investigation of synthesis processes at high temperatures

In our work, we present a method for estimation of the diffusion and reaction rates of synthesis at high temperatures using limited information from laboratory experiments, such as synthesis time and dimensions of reactants. Synthesis by sol-gel and solid-state reactions is considered. The inverse modeling problem is solved for one- and two-dimensional models. Explicit formulas for the diffusion coefficient and reaction rate as functions of temperature are obtained. The activation energies are calculated, and the lower bounds of diffusion and reaction rates are estimated, thus obtaining conditions for occurrence of synthesis.      

Structure-reactivity relationships in organosilicon chemistry revisited

Available quantitative data of the reactivity of organosilicon compounds were subjected to correlation analysis. As an alternative to the carbon chemistry values, the scale of steric constants E _S (Si) can be used for organosilicon compounds and the inductive effect is best expressed by two terms, involving the parameter of electronegativity of substituents. Alkyl substituents contribute to the reactivity exclusively through their steric effects, steric and polar effects in silicon compounds are additive and the resonance effect is insignificant. The correlation analysis can be employed in investigations of organosilicon reactions along with other methods.      

Influence of activated carbon modifications on their catalytic activity in methanol and ethanol conversion reactions

Activated carbons containing different surface functionalities have been investigated as catalysts in conversion reactions of ethanol and methanol. These carbon materials were prepared from Polish brown coal by chemical activation with potassium hydroxide and modified by the oxidation or reaction with ammonia or chlorine. The main process upon ethanol decomposition was its dehydrogenation, while in the process of methanol decomposition only a few samples were catalytically active, and the only product was dimethyl ether (a product of dehydration).      

Physicochemical characteristics of 2-, 3- and 4-methylpyridinium tetrachloroferrates(III)

The crystal structure of 2-methylpyridinium tetrachloroferrate(III) was determined. The iron cation is tetracoordinated by chloride anions, and it adopts a slightly distorted tetrahedral coordination with three angles smaller, two almost equal and one larger than the tetrahedral. The compound is isostructural with its 3-, and 4-methylpyridinium analogues. The thermal properties of 2-, 3- and 4-methylpyridinium tetrachloroferrates(III) have been studied using TG and DSC techniques. The compounds exhibit a high stability in the melt.      

Vibrational calculations in formaldehyde: the CH stretch system

An alternative procedure for the calculation of highly excited vibrational levels in S0 formaldehyde was developed to apply to larger molecules. It is based on a new set of symmetrized vibrational valence coordinates. The fully symmetrized vibrational kinetic energy operator is derived in these coordinates using the Handy expression [Molec. Phys. 61, 207 (1987)]. The potential energy surface is expressed as a fully symmetrized quartic expansion in the coordinates. We have performed ab initio electronic computations using GAMESS to obtain all force constants of the S0 formaldehyde quartic force field. Our large scale vibrational calculations are based on a fully symmetrized vibrational basis set, in product form. The vibrational levels are calculated one by one using an artificial intelligence search/selection procedure and subsequent Lanczos iteration, providing access to extremely high vibrational energies. In this work special attention has been given to the CH stretch system by calculating the energies up to the fifth CH stretch overtone at ∼16000 cm⁻¹, but the method has also been tested on two highly excited combination levels including other lower frequency modes.      

One-pot, three-component condensation of 2-hydroxybenzaldehyde derivatives, primary amines with alkyl isocyanides to N-alkyl-2-(2-hydroxyphenyl)-2-imino-acetamides

One-pot, three-component condensation of 2-hydroxybenzaldehyde derivatives, primary amines with alkyl isocyanides is reported. N-alkyl-2-(2-hydroxyphenyl)-2-iminoacetamide derivatives are generated presumably via the preliminary formation of N, N′-disubstituted benzo[b]furan-2,3-diamines and subsequent oxidation with molecular oxygen.      

Total polyphenolic compounds contents (TPC), total antioxidant activities (TAA) and HPLC determination of individual polyphenolic compounds in selected Moravian and Austrian wines

Wine samples (Grüner Veltliner (GV) and Zweigelt (ZW) from four different geographical regions of Austria and Czech Republic) were analyzed to determine their total phenolic content (TPC) by applying the Folin-Ciocalteau method, total antioxidant activity (TAA) by FRAP (ferric reducing antioxidant power) and DPPH (1,1-diphenyl-2-picryl-hydrazyl) assays, and to identify and quantify eleven phenolic compounds using a HPLC/UV-VIS method.      

Synthesis of 1-aryl-1-phenylpropenes using an alkylation-rearrangement-methylation-isomerization one-pot reaction sequence

(Z/E)-1-(2-Methoxyaryl)-1-phenylpropenes have been prepared in good yields by heating a mixture of a phenolic substrate, cinnamyl chloride, tetramethylammonium chloride and K₂CO3 in polyethyleneglycol at 180°C. The one-pot synthesis proceeds through four discrete reaction steps: alkylation of the phenol with cinnamyl chloride, Claisen rearrangement, O-methylation and double-bond migration. The configuration of one crystalline product was determined using a single-crystal X-ray diffraction analysis. The thermodynamic and structural features of the products were evaluated using computational chemistry techniques.      

Ceramic materials made of CdTe and Cd-Zn-Te nanocrystalline powders

In the present study newly produced semiconductor ceramic nanopowder materials made of CdTe and Cd_1−xZn_xTe (CZT) are considered. Common features and differences in microstructures, phase transformations, grain growth and properties of the ceramic materials of the binary and ternary compositions are studied.      

Use of multivariate statistical techniques to optimize the separation of isoflavones by liquid chromatography

The aim of this paper is to optimize and validate a high performance liquid chromatography (HPLC) method for separation and quantification of five isoflavones. A statistical central composite design was used to separate all peaks. These multivariate procedures were efficient in determining the optimal separation condition using resolution, capacity factor, asymmetry and number of theoretical plates.