α-Trifluoromethyl vinyl acetate. II

Low conversion, low molecular weight homopolymers of α-trifluoromethyl vinyl acetate have been obtained by pyridine initiation and also by employing very large amounts of benzoyl peroxide. Since allylic hydrogens are not present, it appears that the limiting factor in the polymerization of isopropenyl esters is a slow rate of chain growth rather than degradative chain transfer. Copolymerization of the fluoromonomer (M₂) with vinyl acetate (M₁) yields values of r₁ = 0.25 and r₂ = 0.20, and for the fluoromonomer values of 0.069 and 1.51, respectively, for Q and e. Whereas ultraviolet initiation of equimolar mixtures of α-trifluoromethyl vinyl acetate and vinyl acetate yields low molecular weight copolymers, diisopropyl percarbonate-initiated room temperature bulk copolymerizations and emulsion copolymerizations yield polymers of high DP . Differential thermal analysis of an equimolar copolymer of vinyl acetate and the fluoromonomer surprisingly yields a sharp endotherm reminiscent of crystalline polymers. The unhydrolyzed copolymers in acetone and the alcoholyzed copolymers in 0.1N alkali exhibit Huggins k′ values of 0.3–0.4. Like ordinary poly(vinyl alcohol), the polyfluoroalcohols lose viscosity in dilute alkali due to retrograde aldol condensations. The solubilities of the polyfluoroalcohols, together with their thermal behavior, NMR spectrum, polarized infrared spectrum, refractive index, abilities to form visible polarizers, and other properties are also described.     

Structural, optical and photocatalytic studies of Fe doped ZnS nanoparticles

Fe doped ZnS nanoparticles (Zn_1?xFe_xS; where x = 0.00, 0.03, 0.05 and 0.10) were synthesized by a chemical precipitation method. The synthesized products were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope, ultraviolet–visible and photoluminescence spectrometer. The X-ray diffraction and transmission electron microscope studies show that the size of crystallites is in the range of 2–10 nm. Photocatalytic activities of ZnS and 3, 5 and 10 mol% Fe doped ZnS were evaluated by decolorization of methylene blue in aqueous solution under ultraviolet and visible light irradiation. It was found that the Fe doped ZnS bleaches methylene blue much faster than the undoped ZnS upon its exposure to the visible light as compared to ultraviolet light. The optimal Fe/Zn ratio was observed to be 3 mol% for photocatalytic applications.     

Mo<Subscript>6</Subscript>Cl<Subscript>12</Subscript>-Incorporated Sol-Gel for Oxygen Sensing Applications

Excitation of hexanuclear molybdenum complexes such as Mo₆Cl₁₂ and its derivatives in the ultraviolet results in a strongly red-shifted luminescence centered at 750nm. Since oxygen efficiently quenches the luminescence, these thermally stable inorganic complexes are candidate lumophores for real-time, high temperature optical fiber based sensing of oxygen. Sol-gel films containing the acetonitrile complex of Mo₆Cl₁₂ were deposited on quartz substrates by dip coating. After drying, the films were heated at 200^∘C for 1 h. The luminescence lineshapes of films before and after heating were unchanged, indicating that heating did not adversely affect the cluster photophysics. Compared to solutions of the acetonitrile complex, quenching by oxygen was smaller in the as-prepared films, but heating at 200^∘C for 1 h increased the quenching, apparently due to increased oxygen permeability resulting from the loss of water or other small molecules from the matrix. These results confirm the potential of hexanuclear molybdenum complexes such as Mo₆Cl₁₂⋅2CH₃CN as the lumophores in fiber optic oxygen sensors that can operate up to 200^∘C.     

The automatic liquid nitrogen filling system for GDA detectors

An indigenously developed automatic liquid nitrogen (LN2) filling system has been installed in gamma detector array (GDA) facility at Nuclear Science Centre. Electro-pneumatic valves are used for filling the liquid nitrogen into the high purity germanium detector cryostat. The temperature of the out-flowing gas/liquid from the cryostat is monitored using platinum resistor thermometer. The program allows for automatic filling at regular intervals with temperature monitoring from a remote terminal.     

Ester der Imidodiphosphorsäure

Imidodiphosphoric Acid Esters Imidodiphosphoryl tetrachloride reacts with aliphatic alcohols (C₁–C₃) as well as with sodium phenolate to form tetraalkylesters or tetraphenylesters of the imidodiphosphoric acid, resp. The tetraalkylesters (alkyl = methyl, ethyl, n-propyl) are also formed by reaction of trichlorphosphazene phosphoryldichloride, Cl₃P?N? POCl₂, with the corresponding alcohols. The purification of the esters can be reached by destillation of their silyl derivatives followed by desilylation. The esters are associated by intermolecular O…?H…?O hydrogen bonds.     

Versatility of Alternative Reaction Media: Water-Mediated Domino and Green Chemical Synthesis of Pyrimido[1,2-a]benzimidazole Under Nonconventional Conditions

A convenient and clean water-mediated synthesis of a series of 4-amino-2-aryl-1,2-dihydro pyrimido[1,2-a]benzimidazoles (4) is reported using alternative nonconventional energy sources. The products are obtained in shorter times with excellent yields (78–89%) from the multicomponent reaction of 2-aminobenzimidazole (1), malononitrile/ethylcyanoacetate (2a/b), and carbonyl compounds (3). The reaction is found to be general with respect to the cyclic and acyclic carbonyl compounds. The procedure does not involve the use of any additional reagent/catalyst, produces no waste, and represents a green synthetic protocol with high atom economy.     

Investigation of the Reaction of Chloroacetyl Chloride with 1,5-Benzothiazepines: Selective Synthesis of Azeto[2,1-d][1,5]benzothiazepines by Green Chemical Methods and Their Biological Activity

An efficient and exclusive synthesis of the tricyclic azeto[2,1-d][1,5]benzothiazepine ring system has been developed. By use of microwave irradiation in the presence of basic alumina, the reaction time has been brought down from hours to minutes with improved yields in comparison to conventional heating. Antimicrobial screening of the synthesized compounds has shown promising activity.