JOURNAL OF PHYSICAL AND THEORETICAL CHEMISTRY
Year:2011 | Volume:8 | Issue:1|Papers Count:10

The insertion of an olefinic C=C bond into a metal-carbon bond is of potential interest as a preparative route to new products and as results of C-C coupling reactions to organic compounds. The allyl compounds of Mg, react with an olefin by inversion of the allyl group via a six center transition state. These precyclic reactions may be one of the most important classes of organic reactions. The reactions of C3H5MgX (X=F, Cl, Br, I) with ethylene will be discussed in light of computational studies usingab initio methods (RHF/6-31G*//RHF/6-31G* level). The investigation of the structural properties, theoretical thermodynamic and kinetic data i.e. DrG, DG# and rate constants of the reactions at 298oK will be presented.

Two bonding models i.e cumullenic and acetylenic models have been proposed to account for the bonding patterns in linear carbon clusters while the bonding patterns in cyclic and 3D geometries of these clusters have remained ambiguous.This work presents the bonding patterns in various C4 and C5 pure clusters at MP2/aug-cc-pVTZ level of theory. This subject is studied in the light of modern bonding theory known as Quantum Theory of Atoms in Molecules, QTAIM.In linear clusters the ethylene like chemical bonds are reported, while in cyclic and 3D geometries the single and triple C-C bonds are found.

A poly (vinyl chloride) membrane based on a new α-dioxime derivative as membrane carrier was prepared and investigated as a Cr (III) selective electrode. The electrode exhibits a good potentiometric response for Cr (III) over a wide concentration range 1.0×10-6 to 1.0×10-1 M with a slope 19.5±0.5 mV/decade and low detection limit of 8.9×10-7 M. It has a fast response time £15 s. The best performance was observed with the membrance having the PVC-ligand-acetophenone-oleic acid composition 6: 1: 13: 1. The proposed electrode works well in a wide pH range 1.5-5.5. The proposed sensor was successfuly used for the determination of Cr (III) ions in samples and real samples and as indicator electrode in potentiometric titration of Cr (III) ion. The application of this electrode for Cr (III) determination in real samples is described. The results obtained with this procedure are in close agreement with those obtained using AA spectrophotometry.

Potassium Channels allow potassium flux and are essential for the generation of electric current across excitable membranes. Potassium Channels are also the targets of various intracellular control mechanisms; such that the suboptimal regulation of channel function might be related to pathological conditions. Realistic studies of ion current in biologic channels present a major challenge for computer simulation approaches. Molecular dynamics simulations may be used to probe the interactions of membrane proteins with lipids and with detergents at atomic resolution. Examples of such simulations for ion channels and for bacterial outer membrane has already been studied. In this work, to characterize protein behavior, we observed quantities such as gyration radius and energy average. It was studied the changes of these factors for potassium channel Protein in gas, water, Methanol and Ethanol phases with native conformation by Monte Carlo, Molecular and Langevin Dynamics simulations. Monte Carlo simulation is stochastic method and therefore, is the best method to evaluate the radius of gyration in gas phase. when the temperature is increased the kinetic energy is increased too, and its correlation is linear. All the calculations were carried out By Hyperchem 8.0 program. The radius of gyration for different solvent is calculated by VMD 1.8.7 Software. The determination of gyration radius is a spectacular for configuration of a Macromolecule. It also reflects molecular compactness shape. Monte Carlo simulation is the best method to evaluate gyration radius.

Adsorption capacity of 4-chloro-2-nitrophenol (4C2NP) onto nano-TiO2 from aqueous solutions was investigated in a batch system by considering the effects of various parameters like contact time, nano-TiO2 dosage, initial pH and initial 4C2NP concentration. Optimum conditions for 4C2NP adsorption were found to be initial pH» 2, nano-TiO2 dose» 0.01 g and equilibrium time» 1 h. The adsorption kinetic data were analyzed using pseudo-first and pseudo-second order models. It was found that the pseudo-second-order kinetic model was the most appropriate model, describing the adsorption kinetics.The thermodynamic parameters such as DGo, DHo and DSo were computed from the experimental data.These values show that the adsorption of 4C2NP onto nano-TiO2 is spontaneous and endothermic.

Heterogeneous catalytic hydrogenation of cyclohexene, catalyzed by Pt/Al2O3, was carried out in thirteen various solvents (four alcoholic solvents, six aprotic polar solvents and three non polar solvents) at 25oC. Single-parameter correlations of logk vs. normalized polarity parameter (ETN), hydrogen-bond acceptor basicity (b), hydrogen-bond donor acidity (a) and dipolarity/polarizibility (p*) do not give acceptable results. In addition, logk does not show an acceptable dual-parameter correlation with ETN N and a, ETN and b, ETN and p*, a and b, a and p* and b and p*. Like that, three parameter and four parameter correlations of log k vs. solvatochromic parameters don’t give acceptable results. Correlations of log k vs. acceptor number (AN), donor number (DN), relative static permittivity (e) and dipole moment (m) are tested but don’t give reasonable results. However in case of alcoholic solvents, reaction rate constants increase with increasing of hydrogen-bond donor acidity (a), dipolarity/polarizibility (p*), normalized polarity parameter (ETN), relative static permittivity (e), dipole moment (m) and acceptor number (AN) and decrease with increasing of hydrogen-bond acceptor basicity (b) and donor number (DN). These effects are attributed to the non-polar nature of the reactant and competitive adsorption of solvent on catalyst surface.

Density functional theory (DFT) calculations have been performed to investigating the effects of the molecular oxygen impurity on the quadrupole coupling constant (Qcc) parameters of armchair and zigzag boron nitride nanotubes (BNNTs). Optimization processes have been performed to relax the original and impure structures of the investigated BNNTs. Afterwards, the Qcc parameters have been evaluated for the boron and nitrogen atoms of the optimized BNNTs. The results have indicated that the Qcc parameters of boron and nitrogen atoms could detect the effects of oxygen impurity in the structure of BNNTs, in which the changes of those nitrogen atoms close to the impure region are more obvious. The B3LYP and B3PW91 exchange-correlation functional methods and the 6-31G* standard basis set as implemented in the Gaussian 98 package have been employed for performing the calculations.

The photocatalytic degradation of nonionic surfactant Triton X-100 was studied by a batch process using ZnO commercial powders as the catalyst on irradiation with UV light and its behaviour comparatively with respect to ZnO nanoparticles with diameter size 20 nm. The effects of different conditions such as catalyst type, amount of the photocatalyst, pH of the system, initial concentration and electron acceptors were investigated on degradation. The results showed that the photocatalytic degradation of Triton X-100 was strongly influenced by these parameters. Therefore, the best conditions for the photocatalytic degradation of Triton X-100 were obtained.

The term electronegativity was introduced by Linus Pauling, who characterized on the basis of thermodynamic data from the energies of the single bonds. In present study, the Density Functional Theory (DFT) was used to calculate electronegativity of atoms. The base of calculation is similar to Pauling and Mulliken methods. The results indicate that the largest value of electronegativity for Fluorine atom and then plotted the electronegativity values versus to atomic numbers. We have selected scale of electronegativity base on Pauling’s method. Also we presented an empirical formula for electronegativity calculation that the value of the electronegativity is a function of number of valence electron, in addition to ionization potential and electron affinity. Our novel strategy designed by Natural Population Analysis (NPA) method. All calculations were performed using B3LYP method and aug-cc-pVTZ, 6-311++G (2df), SDDALL and LANL2DZ basis set in Gaussian 03W.

Over the past decade, the chemical behavior of flavonoids as antioxidants has become the subject of intense experimental research. In this paper, we use a quantum-chemical approach to shed light on the reactivity of four poly phenols, Benzoic acid, vanilic acid, gallic acid and flavone. In order to establish the most efficient theoretical methodology, different methods, either Hartree–Fock-based or derived from density functional theory, and different basis sets from 6-31G (d) to 6-31G and 3-21G were tested on Benzoic acid, vanilic acid, gallic acid and flavone that it is phenolic compounds. This research showed oxygen atoms have very important role in these molecules.