Radicals generated in linoleic acid and deuterated linoleic acid have been trapped by the spin trap 2-methyl-2-nitroso-propane (MNP) and identified by electron spin resonance (ESR) and ENDOR spectroscopy. The formation of two distinct secondary alkyl radical adducts (one conjugated, the other non-conjugated, as shown by their UV absorption spectra) was demonstrated by 11, 11-dideuterio-9-cis-12-cis-linoleic acid using HPLC and ESR spectroscopy. 相似文献
Active free radicals formed by the electrooxidation of substituted anilines RC6H4NH2 (R = H, p-Br, p-Cl, p-I, p-Me, p-COOH, p-MeCO, p-NO2, m-CO2H, and m-Cl) are trapped by spin trap 2-methyl-2-nitroso propane (MNP). A multiple ESR signal of the solution containing electrolytic aniline and MNP is identified with the spin adduct of MNP and radical cation 1 by theoretical simulation of observed spectrum. Furthermore, ESR spectra of para- or meta-substituted anilines give a reasonable explanation about spin adducts of MNP and the cation 2 or 3 by the same method. 相似文献
The formation of CF3C(O)CF2N(O.)O2CF2C(O)CF3 free radicals upon the UV irradiation of nitropentafluoroacetone (1) in toluene and mesitylene is established by ESR. The most likely cause of their formation is the one-electron oxidation of the solvents by photoexcited1 followed by decay of the radical anion formed from1 with the expulsion of an NO2 anion and attachment of the radical to a molecule of original1. The irradiation of 1 in triethylsilane results in the elimination of a fluoride ion and fixation of a CF3COCFN(O–)O' radical. UV irradiation of ketone1 in pentane results in the abstraction of a hydrogen atom from the solvent and the formation of a CF3COCF2N(OH)O ' radical.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 512–514, March, 1993. 相似文献
Using ESR spectroscopy, the reaction of P(O)(OPri)2 phosphoryl radicals with C60ML2 (M=Pd, Pt) was studied and the spin-adducts formed were shown to be unstable under the reaction conditions. The 5-addition of Pt(PPh3)4 to the dimer of phosphorylfullerenyl radicals results in metal-containing dimers (RO)2(O)PL2MC60-C60ML2P(O)(OR)2, which dissociate when exposed to visible light to afford C60ML2P(O)(OR)2 radicals; ML2 in these complexes is located in different positions in relation to the radical center. As a result, the ESR spectra contain the superposition of at least five signals of radicals that differ in HFS constants andg-factors.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 938–940, May, 1994.The present work was supported by the Russian Foundation for Basic Research (Projects 93-03-18725 and 93-03-4101). 相似文献
The ESR spectra of the radical adducts of the.CF=CFC(CF3)3 and.C(O)CF(CF3)2 radicals with C60 are characterized by hyperfine interaction with the nucleus of the δ-fluorine atom located above the five-membered cycle
in the fullerenyl radical.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1222–1224, June, 1997. 相似文献
The propagation kinetics of isoprene radical polymerizations in bulk and in solution are investigated via pulsed laser initiated polymerizations and subsequent polymer analyses via size‐exclusion chromatography, the PLP‐SEC method. Because of low polymerization rate and high volatility of isoprene, the polymerizations are carried out at elevated pressure ranging from 134 to 1320 bar. The temperatures are varied between 55 and 105 °C. PLP‐SEC yields activation parameters of kp (Arrhenius parameters and activation volume) over a wide temperature and pressure range that allow for the calculation of kp at technically relevant ambient pressure conditions. The kp values determined are very low, e.g., 99 L mol?1 s?1 at 50 °C, which is even lower than the corresponding value for styrene polymerizations. The presence of a polar solvent results in a slight increase of kp compared to the bulk system. The kp values reported are important for determining rate coefficients of other elemental reactions from coupled parameters as well as for modeling isoprene free‐radical polymerizations and reversible deactivation radical polymerization with respect to tailored polymer properties and optimizing the polymerization processes. 相似文献
On dissolution of C60 in concentrated sulfuric acid, ESR spectra of paramagnetic species, which were identified as dimers (C120+) or oligomers (nC60)+, were recorded. The ESR spectra recorded upon the reaction of a toluene solution of C60 with sulfuric acid were assigned to the radical cation C60+.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2373–2376, November, 1998. 相似文献
The electrochemical and chemical oxidation (by hinderedo-benzoquinones or NOClO4) of H2S in nonaqueous solutions (MeCN) proceeds with the donation of one electron. The formation of the unstable radical cation
of hydrogen sulfide was detected by cyclic voltammetry. The radical cation decomposes to form H+ and the HS. radical. The generation of the hydrogen sulfide radical cation was confirmed by ESR spectroscopy in a frozen Freon matrix.
The possibility of using the hydrogen sulfide radical cation in the synthesis of organosulfur compounds under mild conditions
was studied.
The concept of the work was proposed by Prof. O. Yu. Okhlobystin. The first electrochemical experiments were performed when
he was alive.
Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1182–1188, July, 2000. 相似文献
Summary: A novel method for measuring termination rate coefficients, kt, in free‐radical polymerization is presented. A single laser pulse is used to instantaneously produce photoinitiator‐derived radicals. During subsequent polymerization, radical concentration is monitored by time‐resolved electron spin resonance (ESR) spectroscopy. The size of the free radicals, which exhibits a narrow distribution increases linearly with time t, which allows the chain‐length dependence of kt to be deduced. The method will be illustrated using dodecyl methacrylate polymerization as an example.
Two straight lines provide a very satisfactory representation of the chain‐length dependence of kt over the entire chain‐length region (cR = radical concentration). 相似文献
Direct ESR and spin-trapping experiments were used to study the behavior of Nafion, a perfluorinated ionomer membrane used
in fuel cells, when exposed in the laboratory to oxygen radicals produced by Fenton and photo-Fenton reactions. DMPO (5,5-dimethyl-1-pyroline)
was used as the spin trap. The results suggest that the two ESR methods provide complementary information on Nafion fragmentation.
The presence of membrane-derived fragments was suggested indirectly by the presence of a broad signal (line width ≈ 84 G)
after prolonged exposure of the membrane to the Fenton reagent based on Ti(III), and by the DMPO adduct of a carbon-centered
radical in the spin-trapping experiments. The most convincing proof for the presence of perfluorinated radicals was obtained
in Nafion membranes partially neutralized by Cu(II), Fe(II) and Fe(III) upon exposure to UV-irradiation in the presence or
absence of H2O2 (photo-Fenton treatment). Identification of the chain-end radical RCF2CF
2•
with magnetic parameters different to those determined for the chain-end detected in γ-irradiated Teflon, was taken as evidence for the attack of reactive oxygen radicals on the side-chain of the membrane. Additional
support for this suggestion was the detection of the “quartet” ESR signal assigned to the CF3C•O radical, and of the “quintet” ESR signal assigned to the radical centered at the intersection of the main and side chains.
The limitations and advantages of each approach are discussed. 相似文献