Synthesis and reactions of flavazoles

The study deals with the production of l-phenylflavazoles with chloro, amino, hydroxy, chloromethyl, carboxamido, trichloromethyl, N-pyrrolidyl and N-pyrrolidylmethyl groups substituted at position 3. The interconversions of 3-amino, 3-hydroxy and 3-chlorol- phenylflavazoles were also investigated. Further, an unusual phenylation reaction was found to take place if stored or air-oxidised phenylhydrazine was used as the condensing agent for the formation of flavazoles from quinoxaline-2-carboxaldehyde phenylhydrazones. By this phenylation reaction 1,3-diphenyl, l-p-tolyl-3-phenyl, l-p-chlorophenyl-3-phenyl, l-p-bromophenyl- 3-phenyl and l-phenyl-3-p-tolylflavazoles were prepared. In addition to establishing the structure of the phenylation products, the reaction was shown to take place by a free radical mechanism involving phenyl radicals formed from oxidised phenylhydrazine. Also the oxidation, reduction and bromination reactions of l-phenylflavazole were investigated. The product obtained when a mixture of l-phenylflavazole and sodium borohydride in isopropanol was heated under reflux was shown to be 2-anilinoquinoxaline-3-carboxamide which when refluxed with concentrated hydrochloric acid gave the known 2-anilinoquinoxaline. New procedures were worked out for the oxidative cyclisation reactions of quinoxaline-2carboxaldehyde phenylhydrazones to l-phenylflavazoles in excellent yields using azobenzene as a dehydrogenating agent. These cyclisations were also shown to take place, though in low Yield, if the quinoxaline2- carboxaldehyde phenylhydrazones were heated above their melting points in an atmosphere containing oxygen.

Template-Assisted Synthesis and Characterization of Passivated Nickel Nanoparticles

Potential applications of nickel nanoparticles demand the synthesis of self-protected nickel nanoparticles by different synthesis techniques. A novel and simple technique for the synthesis of self-protected nickel nanoparticles is realized by the inter-matrix synthesis of nickel nanoparticles by cation exchange reduction in two types of resins. Two different polymer templates namely strongly acidic cation exchange resins and weakly acidic cation exchange resins provided with cation exchange sites which can anchor metal cations by the ion exchange process are used. The nickel ions which are held at the cation exchange sites by ion fixation can be subsequently reduced to metal nanoparticles by using sodium borohydride as the reducing agent. The composites are cycled repeating the loading reduction cycle involved in the synthesis procedure. X-Ray Diffraction, Scanning Electron Microscopy, Transmission Electron microscopy, Energy Dispersive Spectrum, and Inductively Coupled Plasma Analysis are effectively utilized to investigate the different structural characteristics of the nanocomposites. The hysteresis loop parameters namely saturation magnetization and coercivity are measured using Vibrating Sample Magnetometer. The thermomagnetization study is also conducted to evaluate the Curie temperature values of the composites. The effect of cycling on the structural and magnetic characteristics of the two composites are dealt in detail. A comparison between the different characteristics of the two nanocomposites is also provided