Theoretical Study of Kinetics and Thermodynamics of Hetero Diels-Alder Reaction of Thiazole and Isothiazol with Thiophene-2,5-dione

DFT methods have been used to study the hetero Diels-Alder reaction of thiazole and isothiazole with thiophen-2,5-dione.The thermodynamic and kinetic parameters were calculated.The relative stabilities of the transition structures corresponding to the endo/exo stereoisomers have been rationalized on the basis of the secondary molecular orbital interactions.NBO analysis was carried out to calculate the synchronicity index.It was shown that all reactions are synchronous.A HOMO-LUMO energy gap shows both reactions are normal electron demand.     

Experimental measurement and thermodynamic modeling of liquid-liquid equilibrium for 1-pentanol + water + NaNO3 at 298.15 and 308.15 K

Experimental measurements have been performed for liquid-liquid equilibria in aqueous systems containing 1-pentanol and sodium nitrate at temperatures of 298.15 and 308.15 K and at atmospheric pressure. The results have been modeled using the extended UNIQUAC model and also a modified version of this model. Relevant model parameters have been adjusted using the experimental data. Both models are capable of correlating the experimental data with an average deviation of less than 0.8 weight percent, with the modified model producing slightly better results. The predictive nature of the models has also been verified.     

Catalytic oxidation of urazoles and bis-urazoles to their corresponding triazolinediones using aluminium nitrate and a catalytic amount of silica sulfuric acid

Abstract  

A simple and efficient catalytic oxidation of urazoles and a bis-urazole to the corresponding triazolinediones by treatment with Al(NO₃)₃.9H₂O in the presence of a catalytic amount of silica sulfuric acid is described. A good range of urazole derivatives was selectively oxidized in CH₂Cl₂ at room temperature in good to excellent yields.     

H2SO4/Silicagel: Highly Efficient Catalyst for the Synthesis of α-Aminonitriles Using Trimethysilyl Cyanide

Summary. The multicomponent Strecker reaction using trimethylsilyl cyanide was performed at room temperature and α-aminonitriles were prepared in excellent yields in the presence of a catalytic amount of H₂SO₄ adsorbed on silica gel.     

Interaction of dimethyltin(IV) dichloride with 5′‐IMP and 5′‐UMP

The formation constants of the species formed in the systems H⁺ + dimethyltin(IV) + 5′‐IMP and 5′‐UMP, H⁺ + 5′‐IMP and H⁺ + 5′‐UMP have been determined in aqueous solution in the pH range 1.5–9.5 at constant temperature (25 °C) and constant ionic strength (0.1 mol dm⁻³ NaClO₄), using spectrophotometric and potentiometric techniques. ¹H and ³¹P NMR investigations in aqueous solution confirmed the species formation. The precipitated complexes of IMP and UMP by Me₂Sn(IV)²⁺ at low pH values were characterized by elemental analysis and FTIR spectroscopy methods, the bonding sites of the ligands were determined and ruled out purine and pyrimidine moieties (N‐7 and N‐1 in IMP and N‐3 in UMP, respectively) while a bidentated coordination of the phosphate group is concluded in both cases. Finally, the experiments revealed the existence of complexes with trigonal bipyramidal structures that is in agreement with similar systems resulted previously. Copyright © 2008 John Wiley & Sons, Ltd.     

A survey of interactions in crystal structures of pyrazine‐based compounds

The important role of pyrazine (pz) and its derivatives in fields such as biochemistry and pharmacology, as well as in the study of magnetic properties, is surveyed. Recognition of these properties without extensive investigations into their structural properties is not possible. This review summarizes interactions that exist between these organic compounds by themselves in the solid state, as well as those in coordination polymers with metal ions and in polyoxometalate‐based hybrids. Complexes based on pyrazine ligands can generate metal–organic framework (MOF) structures that bind polyoxometalates (POMs) through covalent and noncovalent interactions. Some biological and magnetic properties involving these compounds are considered and the effect of hydrogen bonding on their supramolecular architectures is highlighted.     

A combination of molecular docking,receptor-guided QSAR,and molecular dynamics simulation studies of S-trityl-l-cysteine analogues as kinesin Eg5 inhibitors

Structural Chemistry - Kinesin Eg5 plays an essential role in the early stages of mitosis, and it is an interesting drug target for the design of potent inhibitors. In this work, combined molecular...     

Production of light olefins from methanol over modified H-ZSM-5: effect of metal impregnation in high-silica zeolite on product distribution

Research on Chemical Intermediates - Improvement of H-ZSM-5 catalyst to convert methanol to light olefins was studied in this research. High-silica H-ZSM-5 zeolite (Si/Al = 200)...     

Preparation and characterization of Fe3O4@Cu-β-CD as a hybrid magnetic catalyst for the synthesis of dihydropyrano[2,3-c]pyrazoles in H2O

Research on Chemical Intermediates - Fe3O4@Cu-β-CD is a hybrid composite with high catalytic activity. Easy separation with an external magnet and recyclability are the advantages of this...     

Modification of Multiple Knot $B$-Spline Wavelet for Solving (Partially) Dirichlet Boundary Value Problem

A construction of multiple knot B-spline wavelets has been given in [C. K. Chui and E. Quak, Wavelet on a bounded interval, In: D. Braess and L. L. Schumaker, editors. Numerical methods of approximation theory. Basel: Birkhauser Verlag; (1992), pp. 57-76]. In this work, we first modify these wavelets to solve the elliptic (partially) Dirichlet boundary value problems by Galerkin and Petrov Galerkin methods. We generalize this construction to two dimensional case by Tensor product space. In addition, the solution of the system discretized by Galerkin method with modified multiple knot B-spline wavelets is discussed. We also consider a nonlinear partial differential equation for unsteady flows in an open channel called Saint-Venant. Since the solving of this problem by some methods such as finite difference and finite element produce unsuitable approximations specially in the ends of channel, it is solved by multiple knot B-spline wavelet method that yields a very well approximation. Finally, some numerical examples are given to support our theoretical results.