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Dimethylformamide Solution (dimethylformamide + solution)
Selected AbstractsSynthesis of 2,3-dihydro-1,3,4-thiadiazole, thiazole, and triazolo[4,3- a]pyrimidine derivatives from ethyl benzoylacetateHETEROATOM CHEMISTRY, Issue 2 2004Nora M. Rateb Thiophene and thiazole derivatives can be obtained from potassium salt of ethyl 3-oxo-3-phenyl-2-[(phenylamino)thioxomethyl]propanoate and ethyl chloroacetate in N,N -dimethylformamide solution under different conditions. 2,3-Dihydro-1,3,4-thiadiazoles and triazolo[4,3- a]pyrimidine were obtained from reaction of hydrazonoyl halides with each of thioanilide and pyrimidine-2-thione, respectively. Structures of the newly synthesized compounds were elucidated on the basis of elemental analysis, spectral data, and alternative synthesis route whenever possible. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:107,113, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10222 [source] Preparation of amphiphilic statistical copolymers of 2-hydroxyethyl methacrylate with 2-diethylaminoethyl methacrylate, precursors of water-soluble copolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 14 2002Gerardo Martinez Abstract Statistical copolymers of 2-hydroxyethyl methacrylate (HEMA) and 2-diethylaminoethyl methacrylate (DEA) were synthesized at 50 °C by free-radical copolymerization in bulk and in a 3 mol L,1N,N,-dimethylformamide solution with 2,2,-azobisisobutyronitrile as an initiator. The solvent effect on the apparent monomer reactivity ratios was attributed to the different aggregation states of HEMA monomer in the different solvents. The copolymers obtained were water-insoluble at a neutral pH but soluble in an acidic medium when the molar fraction of the DEA content was higher than 0.5. The quaternization of DEA residues increased the hydrophilic character of the copolymers, and they became water-soluble at a neutral pH when the HEMA content was lower than 0.25. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2427,2434, 2002 [source] Synthesis of poly[(2-oxo-1,3-dioxolane-4-yl) methyl methacrylate- co -ethyl acrylate] by incorporation of carbon dioxide into epoxide polymer and the miscibility behavior of its blends with poly(methyl methacrylate) or poly(vinyl chloride)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2001Sung-Young Park Abstract This study was related to the investigation of the chemical fixation of carbon dioxide to a copolymer bearing epoxide and the application of the cyclic carbonate group containing copolymer-to-polymer blends. In the synthesis of poly[(2-oxo-1,3-dioxolane-4-yl) methyl methacrylate- co -ethyl acrylate] [poly(DOMA- co -EA)] from poly(glycidyl methacrylate- co -ethyl acrylate) [poly(GMA- co -EA)] and CO2, quaternary ammonium salts showed good catalytic activity. The films of poly(DOMA- co -EA) with poly(methyl methacrylate) (PMMA) or poly(vinyl chloride) (PVC) blends were cast from N,N,-dimethylformamide solution. The miscibility of the blends of poly(DOMA- co -EA) with PMMA or PVC have been investigated both by DSC and visual inspection of the blends. The optical clarity test and DSC analysis showed that poly(DOMA- co -EA) containing blends were miscible over the whole composition range. The miscibility behaviors were discussed in terms of Fourier transform infrared spectra and interaction parameters based on the binary interaction model. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1472,1480, 2001 [source] Glass-Transition Temperature (Tg) of Free-Radically Prepared Polyacrylonitrile by Inverse Gas Chromatography, 2,.MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 17 2002Molecular-Weight Dependence of Tg of Two Different Types of Aqueous Polymers Abstract The molecular-weight dependence of the glass-transition temperature (Tg) of a series of atactic polyacrylonitriles (PAN)s was studied by inverse gas chromatographic (IGC) analysis. PANs having different molecular weights were prepared by either; (i) the addition of isopropyl alcohol as a chain-transfer agent, or (ii) a scission reaction induced by the addition of alkali (NaOH) to a solution (N,N -dimethylformamide solution, at 25,°C) of the resulting polymer. The intrinsic viscosity [,] was in the range of 10.9,0.1 (dl,·,g,1), which corresponds to a viscosity-averaged molecular weight (Mv) of 1,590,000,3,000. As part of the results, a side reaction, which saw the conversion of the nitrile (CN) groups of PAN into amide (CONH2) and/or carboxylic acids (COOH) groups by alkali, was found to occur. The typical molecular-weight dependence of the Tg in free-radically prepared PAN was discussed in connection with a chain-transfer mechanism in an aqueous medium. Molecular-weight dependence of the Tg for PAN (WA). An error bar is given by a short vertical arrow. [source] NMR Quantification of Tautomeric Populations in Biogenic Purine BasesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 9 2009Bartl Abstract Purine bases such as purine, adenine, hypoxanthine, and mercaptopurine are known to exist in several tautomeric forms. Characterization of their tautomeric equilibria is important not only for predicting the regioselectivity of their N -alkylation reactions, but also for gaining knowledge of the patterns with which these compounds of significant biological activity form hydrogen bonds with their biological targets. The tautomeric equilibria of purine and some purine derivatives in methanol and N,N -dimethylformamide solutions were investigated by low-temperature 1H and 13C NMR spectroscopy. The N(7)H and N(9)H tautomeric forms were quantified by integrating the individual 1H NMR signals at low temperatures. The Gibbs free energy differences were calculated and the effects of substitution on the N(7)H/N(9)H ratio discussed. A previously published theoretically predicted mechanism of the tautomeric exchange is compared with our measurements in deuteriated solvents. The influence of concentration on the temperature of coalescence indicates that supramolecular clusters play a significant role in this proton transfer process. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Superhydrophobic Mats of Polymer-Derived Ceramic FibersJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2008Sourangsu Sarkar Solid preceramic polyaluminasilazane was synthesized through the reaction between liquid cyclosilazane and aluminum tri-sec-butoxide at 160°C. Electrospinning of polyaluminasilazane/polyethyleneoxide (1/0.0001 mass ratio) in chloroform solutions generated smooth fibers while the electrospun fibers from the chloroform/N,N -dimethylformamide solutions had submicrometer structures on the fiber surfaces. Smooth and rough SiCNO ceramic fibers were obtained by the pyrolysis of the green fibers with an 80% yield. Superhydrophobic mats of ceramic fibers were fabricated via a chemical vapor deposition of perfluorosilane onto the rough fibers. These superhydrophobic mats possess good chemical and thermal stability. [source] | |||||||||||||