Synthesis of 2,3-disubstituted pyrazines and quinoxalines by Heck cross-coupling reactions of 2,3-dichloropyrazine and 2,3-dichloroquinoxaline. Influence of the temperature on the product distribution

Heck cross-coupling reactions of 2,3-dichloropyrazine provide a convenient approach to 2,3-dialkenyl-, 2-alkenyl-3-alkyl-, and 2,3-dialkylpyrazines depending on the reaction conditions.     

Synthesis of cyclic α-hydrazino acids

Synthesis of five-, six-, seven-, eight-, and nine-membered cyclic α-hydrazino acids from a common starting material ‘diethylmalonate’ with 26, 16, 34, 13.5, and 13.33% overall yields is described. Sequential allylation or homoallylation and electrophilic amination followed by cyclization gave the desired rings. The methyl esters of eight- and nine-membered rings were synthesized by RCM and the corresponding free acids were generated after hydrolysis in the presence of 1 M BBr₃ solution in DCM.     

Effects of monomer concentration on the structure and properties of polybenzidine micro rods

Polybenzidine was synthesized by interfacial polymerization under various monomer concentrations. Effects of monomer concentration on morphology, structure, and properties of polybenzidine were studied by techniques of Fourier Transform Infrared Spectroscopy, Ultraviolet Visible Absorption Spectroscopy, Scanning Electron Microscopy, Transmission Electron Microscopy, X-ray Diffraction, and Cyclic Voltammetry. The results showed that the synthesized polybenzidine with monomer concentration less than 0.15 mol/L were micro rod-like and the surface of the micro rods was smooth and uniform, However, the micro rod-like polybenzidine cannot be obtained under high monomer concentration because of the explosive polymerization. The results of structural analysis indicated that the monomer concentration should not be very high to obtain the polybenzidine with the optimal degree of conjugation and order arrangement of molecular chain. The polybenzidine synthesized in different monomer concentrations showed different electrochemical activities and the sample with the best electrochemical activity was obtained at monomer concentration of 0.02 mol/L.     

Free Abelian 2-form gauge theory: BRST approach

We discuss various symmetry properties of the Lagrangian density of a four- (3+1)-dimensional (4D) free Abelian 2-form gauge theory within the framework of Becchi–Rouet–Stora–Tyutin (BRST) formalism. The present free Abelian gauge theory is endowed with a Curci–Ferrari type condition, which happens to be a key signature of the 4D non-Abelian 1-form gauge theory. In fact, it is due to the above condition that the nilpotent BRST and anti-BRST symmetries of our present theory are found to be absolutely anticommuting in nature. For the present 2-form theory, we discuss the BRST, anti-BRST, ghost and discrete symmetry properties of the Lagrangian densities and derive the corresponding conserved charges. The algebraic structure, obeyed by the above conserved charges, is deduced and the constraint analysis is performed with the help of physicality criteria, where the conserved and nilpotent (anti-) BRST charges play completely independent roles. These physicality conditions lead to the derivation of the above Curci–Ferrari type restriction, within the framework of the BRST formalism, from the constraint analysis. PACS  11.15.-q; 12.20.-m; 03.70.+k     

Differential operators on a polarized abelian variety

Let be an ample line bundle over a complex abelian variety . We show that the space of all global sections over of and are both of dimension one. Using this it is shown that the moduli space of rank one holomorphic connections on a compact Riemann surface does not admit any nonconstant algebraic function. On the other hand, is biholomorphic to the moduli space of characters of , which is an affine variety. So is algebraically distinct from the character variety if is of genus at least one.

     

Projective Structure,Symplectic Connection and Quantization

Let X be a connected Riemann surface equipped with a projective structure . Let E be a holomorphic symplectic vector bundle over X equipped with a flat connection. There is a holomorphic symplectic structure on the total space of the pullback of E to the space of all nonzero holomorphic cotangent vectors on X. Using , this symplectic form is quantized. A moduli space of Higgs bundles on a compact Riemann surface has a natural holomorphic symplectic structure. Using , a quantization of this symplectic form over a Zariski open subset of the moduli space of Higgs bundles is constructed.     

Capillary electrophoretic determination of zinc dimethyldithiocarbamate (Ziram) and zinc ethylenebisdithiocarbamate (Zineb)

A simple and sensitive capillary electrophoretic method was developed for the separation and determination of Ziram and Zineb in boric acid buffer by direct UV absorbance detection at lambda=254 nm. The separation is dependent on pH and nature of the buffer. The detection limits (S/N=3) are 1.88x10(-6) mol/l (0.57 mug/ml) and 2.48x10(-6) mol/l (0.68 mug/ml) for Ziram and Zineb, respectively. The method was successfully applied to the analysis of wheat samples spiked with Ziram and Zineb.     

Quantitative treatment of substituent effects in the polarographic investigations of some potential antineoplastic 2-amino-4-aryl-5-phenylazothiazoles

Polarographic reduction of 2-amino-4-aryl-5-phenylazothiazoles takes place in a single 2-electron transfer, giving a diffusion-controlled irreversible wave in the pH range 2.0-10.0. Substituents in the 4-position of the thiazole moiety shift the half-wave potential through conjugation of the system. A correlation of E(sol;1 2 ) with the Brown and Hammett substituent constant has also been established.