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Different Peroxides (different + peroxide)
Selected AbstractsSynthesis and Characterization of p -[Perfluoro-1-(2-fluorosulfonylethoxy)] ethylated PolystyreneCHINESE JOURNAL OF CHEMISTRY, Issue 4 2003Guan Chuan-Jin Abstract A new fluorinated polystyrene bearing a p -substituted perfluoro[1-(2-fluorosulfonylethoxy)] ethyl group was synthesized via one-electron oxidation of polystyrene by perfluoro [2-(2-fluorosulfonylethoxy)] propionyl peroxide at different peroxide to polystyrene molar ratios. The yield of perfluoroalkylation decreases with the increase of the reactant molar ratio. The modified polymer has been characterized by various techniques: the ring perfluoro[l-(2-fluorosulfonylethoxy)] ethylation has been proved by FT-IR and 19F NMR; the X-ray photoelectron spectra (XPS) show the maximum binding energy of Fls, Ols Cls(two kinds of carbon atoms, namely C-H and C-F) and S2p, respectively; desulfonylation of the fluorinated polystyrene appearing at 217 °C has been found by its thermogravimetric analysis (TGA). The determinations of contact angle, refractive index and glass transition temperature of the modified polymer have disclosed that when the contact angle increases with the increase of the molar ratio, the refractive index and glass transition temperature decrease. The polydispersity values indicate that the degradation of the polymer chains did not occur during the reaction. [source] Kinetics of the thermal decomposition of bis(trifluoromethyl) peroxydicarbonate, CF3OC(O)OOC(O)OCF3INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 1 2003Maximiliano A. Burgos Paci Thermal decomposition of bis(trifluoromethyl) peroxydicarbonate has been studied. The mechanism of decomposition is a simple bond fission, homogeneous first-order process when the reaction is carried out in the presence of inert gases such as N2 or CO. An activation energy of 28.5 kcal mol,1 was determined for the temperature range of 50,90°C. Decomposition is accelerated by nitric oxide because of a chemical attack on the peroxide forming substances different from those formed with N2 or CO. An interpretation on the influence of the substituents in different peroxides on the OO bond is given. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 35: 15,19, 2003 [source] Amine-Catalyzed Asymmetric Epoxidation of ,,,-Unsaturated AldehydesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7 2007Gui-Ling Zhao Abstract The direct organocatalytic enantioselective epoxidation of ,,,-unsaturated aldehydes with different peroxides is presented. Proline, chiral pyrrolidine derivatives, and amino acid-derived imidazolidinones catalyze the asymmetric epoxidation of ,,,-unsaturated aldehydes. In particular, protected commercially available ,,,-diphenyl- and ,,,-di(,-naphthyl)-2-prolinols catalyze the asymmetric epoxidation reactions of ,,,-unsaturated aldehydes with high diastereo- and enantioselectivities to furnish the corresponding 2-epoxy aldehydes in high yield with up to 97:3 dr and 98,% ee. The use of non-toxic catalysts, water and hydrogen peroxide, urea hydroperoxide or sodium percarbonate as the oxygen sources could make this reaction environmentally benign. In addition, one-pot direct organocatalytic asymmetric tandem epoxidation-Wittig reactions are described. The reactions were highly diastereo- and enantioselective and provide a rapid access to 2,4-diepoxy aldehydes. Moreover, a highly stereoselective one-pot organocatalytic asymmetric cascade epoxidation-Mannich reaction, which proceeds via the combination of iminium and enamine activation, is presented. The mechanism and stereochemistry of the amino acid- and chiral pyrrolidine-catalyzed direct asymmetric epoxidation of ,,,-unsaturated aldehydes are also discussed. [source] Methyl methacrylate modification of polyolefin in a batch mixer and a twin-screw extruder experiment and kinetic modelPOLYMER ENGINEERING & SCIENCE, Issue 12 2003Jaehyug Cha Free radical grafting with methyl methacrylate onto molten polypropylene was investigated in both an internal mixer and a modular co-rotating twin-screw extruder. There has been little open literature on melt free radical grafting copolymerization of methyl methacrylate. There is also little information on the evolution of grafting reaction with respect to reaction time in an internal mixer and along the screw axes with methyl methacrylate. The influence of residence time on the degree of grafting in an internal mixer and a twin-screw extruder was studied through measuring reaction yields with respect to reaction time in a mixer and evolution of reaction yield along the screw axis. The degree of grafting increased with initial monomer and peroxide concentration. The grafting reactions with three different peroxides were also investigated. The grafting levels were similar to maleic anhydride and suggested that only an individual methyl methacrylate unit be grafted. The melt viscosity was dramatically reduced with addition of peroxide. A kinetic scheme of our reaction system for methyl methacrylate was proposed and compared with the experimental results. [source] Styrene grafting onto a polyolefin in an internal mixer and a twin-screw extruder: Experiment and kinetic modelPOLYMER ENGINEERING & SCIENCE, Issue 7 2001Jaehyug Cha There has been relatively little effort to quantitatively understand graft copolymerizaution in either batch mixers or twin-screw extruders. Most efforts have concentrated on grafting maleic anhydride, which does not homopolymerize. In this paper we consider grafting with styrene, which may homopolymerize as well as graft. The influence of residence time on degree of grafting in an internal mixer and a twin-screw extruder were studied by measuring reaction yields with respect to reaction time in a mixer and along the screw axis in a twin-screw extruder. The degree of grafting increased with initial monomer and peroxide concentration. Grafting reactions with three different peroxides were also investigated. The degree of styrene grafting in an internal mixer is slightly higher than that in a twin-screw extruder. The rate of reaction along the screw axis in terms of residence time seems higher than for the batch mixer. The melt viscosity dropped dramatically with addition of peroxide. A kinetic scheme is proposed and the experimental results are critically compared with it. [source] | ||||||||||