- Kinetics for the recombination of phenyl radicals
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The rate constant for the C6H5 + C6H5 recombination reaction has been determined in the temperature range 300-500 K using a laser photolysis/mass spectrometric technique. The result is represented by k1 = (1.39 ± 0.11) × 1013e-(56±36)/T cm3/(mol s). In addition, the rate constant for the C6H5 + C6H5NO association reaction was found to be k4 = (4.90 ± 0.19) × 1012e(34±16)/T cm3/(mol s) by the mass balance of the initial concentration of C6H5 radicals. Using the result of k1, previous kinetic data for C6H5 reactions determined by the conventional relative rate method were reanalyzed.
- Park,Lin
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- Reactions of nitrosoarenes with nitrogen monoxide (nitric oxide) and nitrogen dioxide: Formation of diarylnitroxides
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Nitrosoarenes react with nitrogen monoxide (nitric oxide) at room temperature and in aprotic media to afford the corresponding diarylnitroxides by the intermediate formation of N-nitrosoarylnitroxides. However, these latter spin adducts, in contrast with literature reports, have never been detected by us. N-nitrosophenylnitroxide is obtained only in the oxidation of the ammonium salt of N-nitrosophenylhydroxylamine (cupferron) with trace amounts of lead tetraacetate. However, it evolves with time to diphenylnitroxide, as demonstrated by following the reaction course in the ESR cavity. On a macroscale level, the reaction between nitrosobenzene and nitric oxide leads to the formation of N-nitrosodiphenylamine, 4-nitro-N-nitrosodiphenylamine, 4-nitrodiphenylamine and 4,4′-dinitrodiphenylamine, in addition to diphenylnitroxide. Diarylnitroxides are also obtained when nitrosoarenes react with small amounts of nitrogen dioxide; the mechanism of this reaction is proposed and discussed. The structure of 4-nitro-N-nitrosodiphenylamine was determined by X-ray analysis. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Astolfi, Paola,Carloni, Patricia,Damiani, Elisabetta,Greci, Lucedio,Marini, Milvia,Rizzoli, Corrado,Stipa, Pierluigi
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experimental part
p. 3279 - 3285
(2009/04/06)
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- Reactions of N-nitrosodiphenylamine with Grignard reagents. A convenient synthesis of diaryl- and dialkyl nitroxyls
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N-nitrosodiphenylamine reacts with Grignard reagents forming symmetric dialkyl- or diarylhydroxylamines which are quantitatively converted into the corresponding nitroxyls by lead dioxide oxidation.
- Cardellini,Greci,Tosi
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p. 201 - 207
(2007/10/02)
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- Secondary Spin Adducts Derived from Aryl Radicals and 2-Methyl-2-nitrosopropane. Radical Chromato-ESR Spectroscopy and Numerical Decoupling Analysis Studies
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Spin adducts obtained from 2-methyl-2-nitrosopropane (MNP) and phenyl or para-substituted phenyl radicals have been studied by means of radical chromato-ESR spectroscopy.Several previously unknown spin adducts have been isolated and detected in addition to the primary spin adducts of aryl-t-butylaminoxyl radicals.The newly obtained spin adducts have been found to be secondary spin adducts which result from the reaction of the primary spin adducts with aryl radicals.The structures of some of the secondary spin adducts have been shown to be o-(aryl)aryl-t-butylaminoxyl radicals, a variety of sterically hindered aminoxyl radical.This type of aminoxyl radical has been studied for the first time in this work.The hyperfine coupling constants of the spin adducts have been determined using NMR spectroscopy and a numerical decoupling analysis (NDA).The spin density at the meta-protons in these radicals was unusually high.This can be ascribed to the largely steric hindrance between the t-butyl and the ortho-phenyl groups.The formation pathways of these secondary spin adducts have also been revealed.
- Nozaki, Koichi,Naito, Akira,Hatano, Hiroyuki,Okazaki, Satoshi
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p. 113 - 119
(2007/10/02)
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- The reactions of nitrosoarenes with cationic cyclohexadienyl complexes of iron tricarbonyl: an ESR study
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The reactions of nitrosoarenes with the (cyclohexadienyl)Fe(CO)3 cation have been investigated by using electron spin resonance spectroscopy.The radicals produced are nitroxides of the type (OC)3Fe(C6H7)(Ar)N-O* but, in some cases, disproportionation and loss of the metal carbonyl fragment leads to the corresponding C6H5(Ar)N-O* radical.With bulky nitrosoarenes, such as C6Me5NO, isomers are observed in which the aryl ring rotation is slow on the ESR time scale.The analogous reactions with the cyclohexadienyl cation derived from the B ring of (ergosteryl acetate)Fe(CO)3 lead to initial attack not at one of the termini of the delocalized system but rather at the central carbon, i.e., at C-7.Subsequent hydrogen migration leads to the (5,7-diene)Fe(CO)3 complex bearing the arylnitroxide at the 7-position.The mechanisms of these reactions are discussed.Key words: nitrosoarenes, iron cations, ESR.
- Li, Lijuan,Perrier, Richard E.,Eaton, Donald R.,McGlinchey, Michael J.
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p. 1868 - 1877
(2007/10/02)
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- Orientation of Small Moleculles in a Nematic Liquid Crystal as Studied by Electron Spin Resonance
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Based on the measurements of hyperfine splitting constants (hfsc) of small aminoxyl (nitroxide) radicals in the nematic phase of N-4-methoxybenzylidene-4'-n-butylaniline (MBBA) we discussed the relation between the molecular orientation and the molecular shape, especially the contribution of the phenyl groups to the molecular alignments.
- Matsuura, K.,Kotake, Y.,Kuwata, K.
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p. 327 - 334
(2007/10/02)
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- PARTICIPATION OF OXYGEN IN THE FORMATION OF PHOTOINDUCED FORMS IN THE PULSED PHOTOEXCITATION OF 3-HALOGENOCARBAZOLES AND 4-HALOGENODIPHENYLAMINES
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By flash photolysis it was shown that photoinduced forms, which were tentatively assigned the structure of a radical-ion pair of the radical-cation with the superoxide ion, were formed in addition to radical-cations and aminyl and nitroxyl radicals during the photoexcitation of 3-halogencarbazoles and 4-halogendiphenylamines in aerated solutions.
- Frolov, A. N.
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p. 831 - 838
(2007/10/02)
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- ESR Studies of Photochemical Reactions of Diphenylamines, Phenothiazines, and Phenoxazines
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Detailed photochemical reactions of diphenylamines, phenothiazines, and phenoxazines have been studied by the ESR technique.Our results show nitroxide radicals are the stable products of the photooxidation of both diphenylamines and phenothiazines, while cation radicals are the stable product of the photolyzed phenoxazines in the presence of air.
- Lin, Tien-Sung,Retsky, Joel
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p. 2687 - 2689
(2007/10/02)
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- "Spontaneous" Formation of Radicals from Nitroso Compounds. Inadvertent Photolysis vs. Molecule Assisted Homolysis
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The formation of radicals by a "spontaneous" reaction between nitroso compounds and certain organic materials has often been reported in the literature and has generally been ascribed to a process of molecule assisted homolysis (MAH).Some selected "sponta
- Chatgilialoglu, C.,Ingold, K. U.
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p. 4833 - 4837
(2007/10/02)
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- Observations on the Cleavage of the Bismuth-carbon bond in BiV Compounds: a New Arylation Reaction
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Further examples of the selectivity of pentavalent triaryl-organobismuth oxidants are presented; deuterium labelling studies have established that the mechanism of oxidation of allylic alcohols by these reagents involves, to some extent, cleavage of the bismuth-aryl bond; several reactions involving the synthetically useful transfer of an aryl group from bismuth to nitrogen and to carbon are described.
- Barton, Derek H. R.,Lester, David J.,Motherwell, William B.,Papoula, M. Teresa Barros
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p. 246 - 247
(2007/10/02)
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