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Nitroxyl Radical (nitroxyl + radical)

Distribution by Scientific Domains

Polymers and Materials Science	50%
Chemistry	50%

Selected Abstracts

ChemInform Abstract: Selective Electrocatalytic Oxidation of N-Alkyl-N-methylanilines to N-Alkylformanilides Using Nitroxyl Radical.

CHEMINFORM, Issue 32 2001
Yoshitomo Kashiwagi
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: Reactions of Metalated 1-Hydroxy-2,2,4,5,5-pentamethyl-2,5-dihydro-1H-imidazole with Functionalized Nitroxyl Radicals Derived from 2,5-Dihydro-1H-imidazole and 2,5-Dihydro-1H-imidazole 3-Oxide.

CHEMINFORM, Issue 50 2001
V. A. Reznikov
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Effect of hindered piperidine light stabilizer molecular structure and UV absorber addition on the oxidation of HDPE.

JOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 4 2004
Part 2: Mechanistic aspects, electron spin resonance spectroscopy study, molecular modeling
The first in this series of papers explored the effect of the structural characteristics of 2,2,6,6-tetramethylpiperidine-based hindered amine light stabilizers (HALS) on the thermal and photostabilization of high-density polyethylene. In the second part, the energies (stabilities) of the nitroxyl radicals and various intermediate species have been predicted using AccuModel® and related to stabilization performance and electron spin resonance (ESR) spectral data. Nitroxyl radicals with low predicted stability generally afforded improved thermal and photostabilization. ESR spectra were used to obtain values of nitroxyl radical concentration ([>NO·]) and g -factor as a function of pre-aging time for combinations of pre-aged HDPE and >NH HALS. Demethylation reactions of > N-methyl HALS resulted in uselessly weak ESR spectra. The HALS that afforded poor thermal oxidative stabilization gave rise to pronounced minima in [>NO·] that coincided with a maximum in hydroperoxide concentration. The g -factor values indicated that a predominant nitroxyl canonical form generally promoted superior thermal oxidative stabilization, whereas a predominance of the dipolar N·+O, form promoted superior photo-oxidative stabilization. These trends may be related to greater radical-scavenging and peroxide-trapping effects, respectively. Molecular modeling and ESR spectra can therefore provide valuable insight into the effectiveness of HALS and stabilization mechanisms. J. Vinyl Addit. Technol. 10:159,167, 2004. © 2004 Society of Plastics Engineers. [source]

One-Pot Homogeneous and Heterogeneous Oxidation of Glycerol to Ketomalonic Acid Mediated by TEMPO

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 3 2003
Rosaria Ciriminna
Abstract Glycerol, an increasingly abundant by-product of biodiesel production, is selectively converted to ketomalonic acid in one pot at pH 10 using NaOCl as regenerating oxidant in water at 2,°C in the presence of catalytic Br, along with the radical TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl). The reaction can also be conducted at completion over a sol-gel silica glass doped with the nitroxyl radical. Considering the stability and versatility of such doped glasses, these materials show real promise as reusable metal-free catalysts for the conversion of a readily available and renewable biofeedstock into a highly valued compound. [source]

Stereoelectronic effects in radical processes,

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 8-9 2006
Paolo Brandi
Abstract A kinetic study of the H-abstraction reaction from cyclic and acyclic alkylarene substrates by the nitroxyl radical (dubbed BTNO) of 1-hydroxy-benzotriazole (HBT) has been carried out in MeCN solution at 25°C. BTNO was generated from one-electron oxidation of HBT by cerium(IV) ammonium nitrate. The H-abstraction reactivity measured with the cyclic alkylarenes is invariably higher than that with the acyclic counterparts. This is explained as the contribution of hyperconjugation between the aromatic ,-system and the scissile benzylic CH bond of the substrate, which weakens the CH bond in the transition state and promotes its cleavage. Stereoelectronic considerations enable to appreciate why the weakening effect is more pronounced in the cyclic system than in the acyclic counterpart, thereby justifying the higher reactivity of the former. Evidence for the intervention of stereoelectronic effects is embodied by the dissociation energies of the CH bonds, having always lower values for the cyclic substrates investigated. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Synthesis of diblock copolymers by combining stable free radical polymerization and atom transfer radical polymerization

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2006
Yan Shi
Abstract A stable nitroxyl radical functionalized with an initiating group for atom transfer radical polymerization (ATRP), 4-(2-bromo-2-methylpropionyloxy)-2,2,6,6-tetramethyl-1-piperidinyloxy (Br-TEMPO), was synthesized by the reaction of 4-hydroxyl-2,2,6,6-tetramethyl-1-piperidinyloxy with 2-bromo-2-methylpropionyl bromide. Stable free radical polymerization of styrene was then carried out using a conventional thermal initiator, dibenzoyl peroxide, along with Br-TEMPO. The obtained polystyrene had an active bromine atom for ATRP at the ,-end of the chain and was used as the macroinitiator for ATRP of methyl acrylate and ethyl acrylate to prepare block copolymers. The molecular weights of the resulting block copolymers at different monomer conversions shifted to higher molecular weights and increased with monomer conversion. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2468,2475, 2006 [source]

Effect of hindered piperidine light stabilizer molecular structure and UV absorber addition on the oxidation of HDPE.

Novel copolymers via nitroxide mediated controlled free radical polymerization of vinyl chloride

MACROMOLECULAR SYMPOSIA, Issue 1 2003
Thomas Wannemacher
Abstract Controlled free radical polymerization (CFRP) of vinyl chloride (VCM) and copolymerization with several comonomers have been studied in aqueous suspension. Therefore di-tert-butylnitroxide and three novel nitroxyl radicals were used as mediating agents. Copolymerization of VCM with styrene, partly combined with acrylonitrile, maleic acid anhydride and maleic acid imide as well as methyl methacrylate, n-butyl methacrylate, butyl acrylate and butadiene have been achieved, demonstrating an efficient route for novel vinyl chloride copolymer architecture. [source]