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In the present work
as well as HRO. radicals were generated in the photochemical interaction of 1,2-benzanthracene with -ethyl phenyl hydroperoxide /HROOH/ in C6H6 and CCl4 at 304 K.
radicals were trapped by C6H6. The main reaction of HRO. radicals is hydrogen abstraction from the hydroperoxide group of HROOH. Although OH radicals are less selective, the hydrogen abstraction is the main process during their interaction with aromatics in contrast to reactions in aqueous solutions, where addition to the benzene ring is the rate-determining process in CCl4:
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CF3O2CF3 was photolyzed at 254 nm in the presence of CO in 760 torr N2 or air at 296 K in a static reactor. In N2, the products CF3OC(O)C(O)OCF3 and CF3OC(O)O2C(O)OCF3 were detected by FTIR spectroscopy. In air, the only observed products were CF2O and CO2 and a chain process, initiated by CF3O, was invoked for the conversion of CO to CO2. From both product studies, a mechanism for the CF3O initiated oxidation of CO was derived, involving the addition reaction CF3O2 + CO → CF3OC(O). The rate constant for the reaction CF3O + CO at 296 K at a total pressure of 760 torr air was determined to be k(CF3O + CO) = (5.0 ± 0.9) × 10−14 cm3 molecule−1 s−1. © 1997 John Wiley & Sons, Inc. 相似文献
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CIDNP has been studied during thermal decomposition, photolysis, and sensitized photolysis of benzoyl chloroacetyl peroxide. The ratio of the CIDNP intensities for the recombination products benzyl chloride and chloromethyl benzoate is dependent on the mode of decomposition, reflecting the extent of rapid decarboxylation of the primary formed benzoyloxy radicals. 相似文献
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Fatma DEMR 《Turkish Journal of Chemistry》2021,45(2):282
In this study, formation and quantification of mechanochemically generated free radicals of lignin were evaluated after the extraction of lignin from olive seeds and detailed lignin characterization was performed. Lignin was extracted from crushed olive seeds as an insoluble solid using Klason method. Isolated lignin was mechanochemically grinded under cryo conditions using Cryomill and particlesizes were determined by using Zeta Sizer, structural changes were followed by XRD and FTIR-ATR; thermal stabilities were tracked by TGA and DSC. In order to enable solubility demanding studies (such as 1H‑NMR and GPC), acylation of lignin was accomplished. ESR measurements were completed to prove the nature of the radicals. Free radicals cavenging activity of olive seed lignin was determined and quantified using 2-diphenyl-1-picrylhydrazyl (DPPH) method. Number of created mechanoradicals (per gram of olive seed lignin) was calculated from the corresponding UV‑Vis spectra. Finally, morphological changes of the lignin over cryomilling was evaluated using SEM. 相似文献
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Time-resolved infrared spectroscopy (TRIR) and density functional theory (DFT) calculations were used to directly observe and assign the vibrational spectra of the triplet states of visnagin and khellin, and to investigate their electron-transfer chemistry. The TRIR spectra of triplet visnagin and triplet khellin, and of their radical cations and anions, were obtained upon 266 nm laser flash photolysis in acetonitrile and in deuterated acetonitrile. The radical cations were observed in the presence of chloranil, and the radical anions were formed in the presence of NaI and KSCN. The TRIR spectra are in good agreement with the calculated vibrational spectra. We did not observe the related neutral radicals by TRIR spectroscopy upon laser flash photolysis (LFP) of khellin in the presence of hydroquinone, but we found evidence for the formation of semiquinone and neutral visnagin radicals upon LFP of visnagin and hydroquinone. 相似文献
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A. L. Attwood D. M. Murphy J. L. Edwards T. A. Egerton R. W. Harrison 《Research on Chemical Intermediates》2003,29(5):449-465
The formation of a series of oxygen-centred radicals on different TiO2 samples (P25 and two different rutile materials) under various conditions was investigated using X-band c.w. Electron Paramagnetic Resonance (EPR) spectroscopy. The radicals were formed either on thermally-reduced TiO2, or by UV irradiation of the oxide under an oxygen atmosphere. The nature and stability of the radicals was also explored as a function of surface hydration. On thermally reduced TiO2, containing surface and bulk Ti3+ centres, oxygen adsorption at 300 K results in the preferential formation and stabilisation of O2
- anions on the P25 surface, but O- and O3
- anions are generated on the rutile surfaces. Superoxide anions (O-) and trapped holes (O2
-) were also identified after photo-irradiation of the thoroughly dehydrated TiO2 samples under oxygen. The O- anions were only visible at low temperatures under continuous irradiation, while the O2
- anions were stable for days at 300 K. By comparison, on fully hydrated surfaces, no stable oxygen centred radicals could be detected on P25, while O2
- anions were easily observed on the rutile surfaces. On partially hydrated P25, the O-, O2
- and HO2 anions were detected after UV irradiation at 77 K; all radicals decayed upon warming to 298 K. On partially hydrated rutile, the O- and O2
- anions were detected and, unlike the case for P25, were found to be stable for days under the same conditions. The results illustrate the varied formation and stability of the oxygen centred radicals on TiO2 surfaces depending on the pretreatment conditions. 相似文献
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The energies, geometric parameters, spin densities, and HFC constants of the Mg-centered radicals •MgH, •MgOH, •MgMe, and monovalent magnesium aqua complexes Mg(H2O)n
+ (n = 0–3) were calculated using the density functional theory. As n increases, the HFC constants decrease for Mg atoms and increase for O atoms. The theoretical HFC constants in the Mg-centered
radicals are in good agreement with experimental data.
Published In Russian In Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, Pp. 861–865, May, 2007. 相似文献
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A series of highly diastereomerically enriched 1,5-dimethyl-, 2,5-dimethyl-, and 3,5-dimethyl-N-benzyl-5-nitro-4-(diphenylphosphatoxy)hexylamines were exposed to tributyltin hydride and AIBN in benzene at reflux. The ensuing reactions, interpreted in terms of radical denitration, radical ionic fragmentation, and nucleophilic substitution, lead to the formation of pyrrolidines with moderate to high diastereoselectivity. In five out of the six cases, the diastereoselectivity is best interpreted by backside attack by the amine on the initial contact ion pair generated by radical ionic fragmentation. In the exception that proves the rule, this mode of attack is disfavored by 1,3A strain in the initial contact ion pair, resulting in equilibration and subsequent attack on the opposite face. 相似文献
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