Electrochemical deposition of copper on steel from a solution of diacido-1,3-propylenediamine-N,N′-diacetato-N,N′-dipropionate cuprate(II)

The possibility of obtaining smooth homogeneous copper coatings with good adhesion and homogeneous copper coatings with poor adhesion by electrochemical deposition of copper on steel from a solution of nontoxic copper(II) complex with the ligands, 1,3-propylenediamine-N,N′-diacetato-N,N′-di-3-propionic acid, was analyzed. For both types of coatings, the optimum composition of the solution and the optimum deposition conditions were determined.     

Bis(PheOH) maleic acid amide-fumaric acid amide photoizomerization induces microsphere-to-gel fiber morphological transition: the photoinduced gelation system

The photoinduced gelation system based on 1 (non-gelling) to 2 (gelling) molecular photoisomerization in water results by microspheres (1) to gel fibers (2) transformation at the supramolecular level.     

Ground-state properties of benzenoid hydrocarbons by simple bond orbital resonance theory approach

π-electron energies and bond orders of benzenoid hydrocarbons with up to five fused hexagons have been considered by the simple Bond Orbital Resonance Theory (BORT) approach. The corresponding ground states were determined according to four BORT models. In the first three models a diagonalisation of the Hückel-type Hamiltonian was performed in the bases of Kekulé, of Kekulé and mono-Claus and of Kekulé and Claus resonance structures, respectively. In the fourth model a simple BORT ansatz was used. According to this ansatz, the ground state is a linear combination of the positive Kekulé structures, all with equal coefficients. It was shown that π-electron energies and bond orders obtained by these models correlate much better with the PPP energies and bond orders than with the Hückel energies and bond orders. This indicates that a simple BORT approach is quite reliable in predicting the more sophisticated PPP results. Concerning the relative performance of the four BORT models, the best results were obtained with the BORT ansatz. The performance deteriorates with the expansion of the basis set. This is attributed to the fact that in these models the improvement of the basis set is not accompanied with the corresponding improvement of the Hamiltonian. Comparing the BORT-ansatz bond orders with the Pauling bond orders, it was shown that BORT-ansatz bond orders correlate much better with the PPP bond orders. This revised version was published online in July 2006 with corrections to the Cover Date.     

Modification of solids with volatile organics III: Natural zeolites

Summary The effect of pre-adsorbed benzene and ethanol on the adsorptive properties of natural zeolite (clinoptilolite) has been studied by gas-solid chromatography. It has been shown that modification of the solid surface by volatile organics has a significant influence on the adsorptive properties. The modification is of the same order as the more difficult modification by inorganics, as illustrated here by clinoptilolite modification with Co²⁺. Energy distribution of surface adsorptive sites appears to be continuous and confirms previous finding that only a small proportion of active sites is responsible for most adsorbate retention. Part II reference [4]     

Hybridization in some macrocyclic polyacetylenes

The hybridization in several cyclic polyacetylene compounds has been calculated by the maximum overlap method, assuming planar and non-planar geometries of the molecules. In the planar configuration the hybrids describing the molecular skeleton deviate from the corresponding bond directions. We have a few “bent” bonds, but in contrast to the situation in small rings, here the deviation angles are negative, i.e., the hybrids point toward the inside of the ring. Non-planar structures in which acetylene groups are kept in a plane and CCH₂ or CH₂ groups are displaced out of the plane show less deviation from the bond directions of bent bonds. Furthermore, the deviation angles decrease with an increase in the out-of-plane displacement of methylene groups. Finally, when the angle of bending of the molecules approaches 50°, the deviation vanishes, predicting a puckered conformation for the molecules. Correlation between CC stretching vibration frequencies and the corresponding CC bond overlap is discussed.     

Kinetic Determination of Microquantities of Rutin by Perturbation of the Bray-Liebhafsky Oscillatory Reaction in an Open System

A kinetic method is described for the microquantitative (microconcentration/microvolume) determination of rutin based on potentiometric monitoring of the concentration perturbations of the Bray-Liebhafsky (BL) oscillatory reaction being in a non-equilibrium stationary state close to a bifurcation point. The experiments are carried out in an open reactor. The response of the matrix system to perturbations by different concentrations of rutin ethanolic solutions is followed by a Pt-electrode. In the concentration range between 7.8×10^–8moldm^–3 and 9.1×10^–6mol dm^–3, we found a linear dependence of the maximal potential shift, E_m, on the logarithm of the rutin concentrations. The unknown concentrations can be determined from the calibration curve up to an accuracy of ±5%. The detection limit is 3.6×10^–8mol dm^–3. The amount of required sample can be as small as 10µL.     

A new approach to predict the biological activity of molecules based on similarity of their interaction fields and the logP and logD values: application to auxins

The activity of a biological compound is dependent both on specific binding to a target receptor and its ADME (Absorption, Distribution, Metabolism, Excretion) properties. A challenge to predict biological activity is to consider both contributions simultaneously in deriving quantitative models. We present a novel approach to derive QSAR models combining similarity analysis of molecular interaction fields (MIFs) with prediction of logP and/or logD. This new classification method is applied to a set of about 100 compounds related to the auxin plant hormone. The classification based on similarity of their interaction fields is more successful for the indole than the phenoxy compounds. The classification of the phenoxy compounds is however improved by taking into account the influence of the logP and/or the logD values on biological activity. With the new combined method, the majority (8 out of 10) of the previously misclassified derivatives of phenoxy acetic acid are classified in accord with their bioassays. The recently determined crystal structure of the auxin-binding protein 1 (ABP1) enabled validation of our approach. The results of docking a few auxin related compounds with different biological activity to ABP1 correlate well with the classification based on similarity of MIFs only. Biological activity is, however, better predicted by a combined similarity of MIFs + logP/logD approach.     

Determination of boron in nuclear materials by isotope dilution technique. Part I

Summary The application of the mass-spectrometric stable-isotope dilution technique for the determination of microgram and submicrogram quantities of boron in nuclear materials is described. An adequate amount of spike solution (enriched in¹⁰B) is added to the sample and the mixture is treated chemically to ensure isotopic equilibration. Boron is then separated as methyl borate by distillation from phosphoric acid and converted into sodium tetraborate suitable for isotopic analysis by surface ionization in a mass spectrometer. The results for boron content in a standard boric acid solution, reagents, ammonium diuranate, uranium dioxide, sintered pellets of UO₂ and uranyl nitrate are given. Owing to the simplicity, accuracy and high precision a possible application of the method would be its use for routine boron determinations in a natural uranium processing plant and/or as a standard method for intercomparison with other analytical methods.

---

Zusammenfassung Die Anwendung der massenspektrometrischen Isotopenverdünnungsmethode auf die Borbestimmung im Bereich von Mikrogramm und darunter in Reaktormaterialien wurde beschrieben.Eine entsprechende Menge von angereichertem¹⁰B wird einer Probe zugegeben und die Mischung zur Herstellung des Isotopengleichgewichtes chemisch behandelt. Das Bor wird dann als Methylborat durch Destillation aus der phosphorsäurehaltigen Lösung abgetrennt und zum Zweck einer massenspektrometrischen Isotopenanalyse in Natriumtetraborat umgesetzt.Der Borgehalt in H₃BO₃-Standardlösungen, Reagenzien, Ammoniumdiuranat (ADU), UO₂, gesinterten UO₂-Pastillen und Uranylnitrat wird angegeben. Wegen der Einfachheit, Genauigkeit und Empfindlichkeit könnte diese Methode sowohl für die routinemäßige Borbestimmung bei der Herstellung von Brennstoffelementen mit natürlichem Uran als auch für die Standardisierung analytischer Methoden angewandt werden.

     

Theoretical study of cyclic conjugation in phenes: Some hitherto unnoticed features

Summary Cyclic conjugation in phenes is examined by means of theBosanac-Gutman-Aihara method. In contrast to the predictions based on the analysis ofKekulé orClar structures, we find that when going along the hexagons of a phene molecule, cyclic conjugation varies in a rather non-uniform manner. In contrast to a number of other homologous series of benzenoid hydrocarbons, the intensity of cyclic conjugation in phenes increases when going towards the center of the molecule.

---

Theoretische Untersuchung der cyclischen Konjugation in Phenen: Einige bisher unbekannte Eigenschaften

Zusammenfassung Die cyclische Konjugation in Phenen wird mittels derBosanac-Gutman-Aihara-Methode untersucht. Im Gegensatz zu auf der Analyse vonKekulé- oderClar-Strukturen beruhenden Voraussagen variiert die cyclische Konjugation entlang der Sechsecke eines Phenmoleküls ziemlich unregelmäßig. Anders als bei anderen homologen benzenoiden Kohlenwasserstoffen nimmt bei Phenen die Intensität der cyclischen Konjugation zum Zentrum des Moleküls hin zu.

     

Investigation of isothermal bulk polymerization ofo-alkyaryl methacrylates by DSC

The kinetics of the AIBN-initiated free radical bulk polymerization of fiveo-alkylphenyl methacrylates was studied by means of DSC in the temperature range 353–373 K, and the enthalpy of polymerization, the overall reaction rate constant and the activation energy were determined. The results were compared with those published recently on correspondingp-alkylaryl methacrylates. All measured reaction rate constants were found to increase with increasing temperature and to decrease with increasingo-alkyl substituent mass and size. It was shown thato-substituents influence the rates of polymerization to a greater extent thanp-substituents. At about 373 K, all differences in rate, most probably resulting from steric hindrance caused by the alkyl groups, disappear in both series, a phenomenon earlier observed for dimethyl phenyl methacrylates.This work was supported by the Ministry of Science of the Republic of Serbia.