- Synthesis of poly(vinyl acetate) and poly(vinyl alcohol) containing block copolymers by combination of cobalt-mediated radical polymerization and ATRP
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Poly(vinyl acetate) (PVAc) chains of a low polydispersity (M w/Mn ~ 1.1-1.2) have been prepared by cobalt-mediated radical polymerization of vinyl acetate (VAc). They have been end-capped by an activated bromide by addition of an α-bromoester or an a-bromoketone containing nitroxide and converted into effective macroinitiators for the atom transfer radical polymerization of styrene (Sty), ethyl acrylate, and methyl methacrylate. Because each block is formed by a controlled process, well-defined PVAc containing diblock copolymers are easily prepared. The PVAc-b-PS copolymers synthesized from α-bromoketone end-capped PVAc can be converted into well-defined poly(vinyl alcohol)-b-polystyrene amphiphiles by methanolysis of the poly(vinyl acetate) block. Self-association of an amphiphilic poly(vinyl alcohol)(3500)-b-polystyrene(16 600) in a (4/1) water/tetrahydrofuran mixture results in the formation of vesicles as observed by transmission electron microscopy.
- Debuigne, Antoine,Caille, Jean-Raphael,Willet, Nicolas,Jerome, Robert
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Read Online
- Kinetics and thermodynamics of reversible disproportionation-comproportionation in redox triad oxoammonium cations - Nitroxyl radicals - Hydroxylamines
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Kinetics and equilibrium of the acid-catalyzed disproportionation of cyclic nitroxyl radicals R2NO· to oxoammonium cations R2NO+ and hydroxylamines R2NOH is defined by redox and acid-base properties of these compounds. In a recent work (J. Phys. Org. Chem. 2014, 27, 114-120), we showed that the kinetic stability of R2NO· in acidic media depends on the basicity of the nitroxyl group. Here, we examined the kinetics of the reverse comproportionation reaction of R2NO+ and R2NOH to R2NO· and found that increasing in -I-effects of substituents greatly reduces the overall equilibrium constant of the reaction K4. This occurs because of both the increase of acidity constants of hydroxyammonium cations K3H+ and the difference between the reduction potentials of oxoammonium cations ER2NO+/R2NO· and nitroxyl radicals ER2NO·/R2NOH. pH dependences of reduction potentials of nitroxyl radicals to hydroxylamines E1/3σ and bond dissociation energies D(O-H) for hydroxylamines R2NOH inwater were determined. For a wide variety of piperidine- and pyrrolidine-1-oxyls values of pK3H+ and ER2NO+/R2NO· correlate with each other, as well aswith the equilibriumconstants K4 and the inductive substituent constants ωI. The correlations obtained allowprediction of the acid-base and redox characteristics of redox triads R2NO·-R2NO+-R2NOH.
- Sen, Vasily D.,Tikhonov, Ivan V.,Borodin, Leonid I.,Pliss, Evgeny M.,Golubev, Valery A.,Syroeshkin, Mikhail A.,Rusakov, Alexander I.
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supporting information
p. 17 - 24
(2015/03/03)
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- Synthesis of novel bicyclic nitroxides using partial favorskii rearrangement
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3-Bromo-2,2,6,6-tetramethyl-4-oxopiperidine-1-oxyl was reacted with several C-nucleophiles to give novel bicyclic pyrrolidine nitroxides through partial Favorskii rearrangement. Further reduction with sodium borohydride gave spin probes with free hydroxyl groups and under harsh reduction conditions allowed the Favorskii rearrangement to proceed to completion. Georg Thieme Verlag Stuttgart.
- Babi?, Andrej,Pe?ar, Slavko
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scheme or table
p. 1155 - 1158
(2009/04/07)
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- HYDROXYLAMINE COMPOUNDS AND METHODS OF THEIR USE
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The present disclosure provides compounds that include hydroxylamines of formula (I) or (II), pharmaceutical compositions, and methods for their use. The methods utilize hydroxylamine compounds and/or their pharmaceutical compositions for the treatment of angiogenesis, hepatitis, complement-mediated pathologies, drusen-mediated pathologies, macular degeneration and certain other ophthalmic conditions, inflammation, arthritis, and related diseases and for the inhibition of complement activation.
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Page/Page column 62
(2008/12/08)
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- A Study of the Favorskii Rearrangement with 3-Bromo-4-oxo-2,2,6,6-tetramethylpiperidin-1-oxyl
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Favorskii rearrangement reactions of the title compound with sodium hydroxide, sodium ethoxide, ammonia, several aliphatic amines, and ethyl sodiomalonate resulting in pyrrolidine nitroxyl radicals are described.
- Sosnovsky, George,Cai, Zhen-wei
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p. 3414 - 3418
(2007/10/02)
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