Spin Trapping

Alberti, Angelo; Macciantelli, Dante

doi:10.1002/9780470432235.ch8

Cited by 15 publications

(16 citation statements)

References 10 publications

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“…Most probably, under the given experimental conditions, the superoxide radical anions are preferably transformed to hydrogen peroxide by a disproportionation with protons [24,26,67]. Moreover, a significantly lower rate constants for the addition of O 2 •− / • O 2 H to the nitrone spin traps may cause the limited production of spin-adducts [46,48]. The rapid transformation of superoxide radical anions, as well as their very slow reaction with nitrone spin traps caused that at room temperature in aerated aqueous TiO 2 suspensions superoxide detection using conventional spectroscopic techniques failed, and only chemiluminescence with luminol or luciferin analog was applied as a suitable experimental method [68,69,70].…”

Section: Resultsmentioning

confidence: 99%

“…Spin traps possessing N -oxide and nitrone groups are mainly applied in the identification of hydroxyl radicals generation, as well as other oxygen-, nitrogen- and sulfur-centered reactive radicals, however the information on the structure of carbon-centered radicals trapped with these agents is limited, and the application of nitroso spin traps is necessary to bring the knowledge on other nuclei in the vicinity of the trapped carbon [46,47]. Successful assignment of measured EPR spectra of spin-adducts requires a thorough interpretation of the acquired data and careful choice of the spin trapping agent for the specific experimental conditions [48].…”

Section: Introductionmentioning

confidence: 99%

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Radical Intermediates in Photoinduced Reactions on TiO2 (An EPR Spin Trapping Study)

2014

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Abstract:The radical intermediates formed upon UVA irradiation of titanium dioxide suspensions in aqueous and non-aqueous environments were investigated applying the EPR spin trapping technique. The results showed that the generation of reactive species and their consecutive reactions are influenced by the solvent properties (e.g., polarity, solubility of molecular oxygen, rate constant for the reaction of hydroxyl radicals with the solvent). The formation of hydroxyl radicals, evidenced as the corresponding spin-adducts, dominated in the irradiated TiO2 aqueous suspensions. The addition of 17 O-enriched water caused changes in the EPR spectra reflecting the interaction of an unpaired electron with the 17 O nucleus. The photoexcitation of TiO2 in non-aqueous solvents (dimethylsulfoxide, acetonitrile, methanol and ethanol) in the presence of 5,5-dimethyl-1-pyrroline N-oxide spin trap displayed a stabilization of the superoxide radical anions generated via electron transfer reaction to molecular oxygen, and various oxygen-and carbon-centered radicals from the solvents were generated. The character and origin of the carbon-centered spin-adducts was confirmed using nitroso spin trapping agents.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Radical Intermediates in Photoinduced Reactions on TiO2 (An EPR Spin Trapping Study)

2014

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“…Nitrosobenzene (NB) was selected as reagent to create a persistent free radical specie (Alberti and Macciantelli 2009) derived from the homolysis of the O-O bond of the EO-SOZ in order to record the relative ESR spectrum. Unexpectedly, when nitrosobenzene was mixed with a partially ozonized sample EO-SOZ a clear ESR signal was obtained immediately after mixing without any thermal or light activation.…”

Section: Spin Trap Experiments and Electron Spin Resonance Of Ethyl Olmentioning

confidence: 99%

Ethyl Oleate and Ethyl Elaidate Ozonides: Thermal Decomposition and Photolysis

Cataldo¹

2015

Ozone: Science & Engineering

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Highly pure ethyl oleate and ethyl elaidate were ozonized to their secondary ozonides (respectively EO-SOZ and EE-SOZ). The decomposition enthalpies of EO-SOZ and EE-SOZ were determined by DSC (Differential Scanning Calorimetry) and found, respectively, at -266 kJ/mol and -264 kJ/mol, a value much closer to the theoretically calculated upper limit of -278 kJ/mol than the decomposition enthalpy of -243 kJ/mol measured on EO-SOZ prepared from an ethyl oleate sample conforming to the European Pharmacopoeia. Although a considerable amount of heat was liberated, EO-SOZ and EE-SOZ cannot be defined as explosive based on their DSC traces at a heating rate of 10 • C/min. Pure EO-SOZ and EE-SOZ show a decomposition peak at the DSCs of 137 • C and 139 • C, respectively. The thermal decomposition of EO-SOZ and EE-SOZ was studied also by FT-IR spectroscopy showing that the decomposition involves the loss of the ozonide infrared band at 1110 cm −1 and the formation of the expected decomposition products (pelargonic acid, pelargonaldehyde, ethyl azelate, etc.). The kinetics of the photochemical decomposition of EO-SOZ and EE-SOZ were studied by FT-IR spectroscopy, and the relative rate constants were determined. EO-SOZ when overozonized forms a spin adduct with nitrosobenzene and the relative nitroxyl radical was clearly detected by the Electron Spin Resonance (ESR). Secondary ozonation products known as trioxides may be responsible for these adducts.

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“…The formation of paramagnetic intermediates upon UVA irradiation of the 10-ethyl-7-oxo-7, 10-dihydropyrido[2,3- f ]quinoxaline derivatives studied was monitored in situ by a well-established EPR spin trapping technique [57]. The photoinduced production of singlet oxygen during the excitation of quinoxalines was followed by the oxidation of a stericaly hindered amine 4-oxo-2,2,6,6-tetramethylpiperidine (TMPO, Merck-Schuchardt, Hohenbrunn, Germany) [51,52].…”

Section: Methodsmentioning

confidence: 99%

Fused-Ring Derivatives of Quinoxalines: Spectroscopic Characterization and Photoinduced Processes Investigated by EPR Spin Trapping Technique

et al. 2014

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10-Ethyl-7-oxo-7,10-dihydropyrido[2,3-f]quinoxaline derivatives, synthesized as promising biologically/photobiologically active compounds were characterized by UV/vis, FT-IR and fluorescent spectroscopy. Photoinduced processes of these derivatives were studied by EPR spectroscopy, monitoring in situ the generation of reactive intermediates upon UVA (λ max = 365 nm) irradiation. The formation of reactive oxygen species and further oxygen-and carbon-centered radical intermediates was detected and possible reaction routes were suggested. To quantify the investigated processes, the quantum yields of the superoxide radical anion spin-adduct and 4-oxo-2,2,6,6-tetramethylpiperidine N-oxyl generation were determined, reflecting the activation of molecular oxygen by the excited state of the quinoxaline derivative.

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Spin Trapping

Cited by 15 publications

References 10 publications

Radical Intermediates in Photoinduced Reactions on TiO2 (An EPR Spin Trapping Study)

Radical Intermediates in Photoinduced Reactions on TiO2 (An EPR Spin Trapping Study)

Ethyl Oleate and Ethyl Elaidate Ozonides: Thermal Decomposition and Photolysis

Fused-Ring Derivatives of Quinoxalines: Spectroscopic Characterization and Photoinduced Processes Investigated by EPR Spin Trapping Technique

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