Trapping electron spin resonance

It is probably now widely accepted that the high temperatures and pressures generated by cavitation are sufficiently extreme to initiate radical formation and reaction. Indeed, spin trap electron spin resonance techniques have been employed to confirm the presence of radicals in some sonochemical experiments. Hydrogen and hydroxyl radical formation due to ultrasound has been positively identified by ESR measurements, and in the relevant reactions are now believed to be formed through thermal dissociation of water molecules at the temperatures generated within the cavitating bubble [31]. 

The nature of the intermediates impHcated in the photooxidation of water with Ti02 has been identified in several reports using spin traps by the electron spin resonance (esr) technique under ambient conditions (53). No evidence for OH species, even at 4.2 K, was found (43), but the esr signal... 

Further aspects of the reaction of aromatic tertiary hydroxyl amines have been examined by more sophisticated techniques [49]. 2-Methyl-2-nitrosopropane was used as a radical trap, and the endgroups on PMMA resulting from its addition were detectable by ultraviolet spectroscopy. Electron spin resonance results on the same system have also been reported [50]. 

Although Otsu et al. [12] have studied the BPO-DMA system by electron spin resonance (ESR) technique and trapped the aminomethyl radical, there is still a lack of direct proof of the above second step, particularly concerning the behavior of the aminium radical salt. We [13] have proposed the aminium radical salt with purple color through this reaction of DMT with CCI4 in the presence of O2 following the displacement reaction as ... 

Despite their short half-lives, it is possible to detect free radicals in biological tissues by the addition of nonradicals such as nitrones or nitroso compounds, which act as spin traps by forming relatively stable free radicals on reaction with the endogenous radical species. Utilizing the technique of electron spin resonance (e.s.r.) spectroscopy, we have demonstrated ROM generation by human rheumatoid synovium when subjected to cycles of hypoxia/normoxia in vitro. Using 3,5-dibromo-4-nitroso-benzenesulphonate (DBNBS) as a spin trap, a... 

X-Ray irradiation of quartz or silica particles induces an electron-trap lattice defect accompanied by a parallel increase in cytotoxicity (Davies, 1968). Aluminosilicate zeolites and clays (Laszlo, 1987) have been shown by electron spin resonance (e.s.r.) studies to involve free-radical intermediates in their catalytic activity. Generation of free radicals in solids may also occur by physical scission of chemical bonds and the consequent formation of dangling bonds , as exemplified by the freshly fractured theory of silicosis (Wright, 1950 Fubini et al., 1991). The entrapment of long-lived metastable free radicals has been shown to occur in the tar of cigarette smoke (Pryor, 1987). 

Electron spin resonance (ESR) measures the trapped electron population in a lattice, which is directly related to the amount of ionizing radiation received by the sample since its formation. The total radiation dose received by the sample is estimated from the ESR... 

Harbour, J.R. and Bolton, J.R. 1975. Superoxide formation in spinach chloroplasts electron spin resonance detection by spin trapping. Biochemical and Biophysical Research Communications 64 803-807. 

Although it is very hard to observe the absorption spectrum of eh when metal is dissolved in water because of its high reactivity, some attempts were made in water and ice (Jortner and Stein, 1955 Benett et al., 1964, 1967). Furthermore ESR (electron spin resonance) studies revealed that the trapped or solvated electron in ice interacts with six equivalent protons, thus ruling out H20-. 

J. Vasquez-Vivar, N. Hogg, K.A. Pritchard, and B. Kalyanaraman, Superoxide anion formation from ludgenin an electron spin resonance spin-trapping study. FEBS Lett. 403, 127—130 (1997). 

The scavenging ability toward O2 can also be measured by using electron spin resonance (ESR) spectrometry. The 02 anion is trapped with 5,5-dimethyl-1-pyrroline TV-oxidc (DMPO), and the resultant DMPO-OH adduct is detected by ESR using manganese oxide as internal standard. Noda and others (1997) used this technique to evaluate antioxidant activities of pomegranate fruit extract and its anthocyanidins (delphinidin, cyanidin, and pelargonidin). 

In order to identify organic free - radicals present at quantifiable concentrations during the sonication of PCBs, we employed Electron Spin Resonance (ESR) with a spin trap, N-t-butyl-a-phenyl-nitrone (PBN). PBN reacts with the reactive free - radicals to form more stable spin-adducts, which are then detected by ESR. The ESR spectrum of a PBN spin adduct exhibits hyperfine coupling of the unpaired election with the 14N and the (3-H nuclei which leads to a triplet of doublets. The combination of the spin-adduct peak position and peak interval uniquely identifies the structure of a free-radical. 

Panchenko, A., Dilger, H., Kerres, J., Hein, M., Ullrich, A., Kaz, T. and Roduner, E. 2004. In situ spin trap electron paramagnetic resonance study of fuel ceU processes. Physical Chemistry Chemical Physics 6 2891-2894. 

Electron spin resonance (ESR) spectroscopy can be advantageously used to measure the radical concentrations of the nitroxide radicals (XV and XVI) produced, since these are much more stable then the R- radicals. Of greater importance, ESR can be used to determine the structure of R% since the ESR of the nitroxide radical is quite sensitive to the structure of R. (For this purpose, nitroso spin traps are more useful, since the R group in the nitroxide radical is nearer to the lone electron.) This can allow a determination of the structures of radicals first formed in initiator decomposition, the radicals that actually initiate polymerization (if they are not identical with the former) as well as the propagating radicals [Rizzardo and Solomon, 1979 Sato et al 1975],... 

Thermal decomposition of allylbenzene ozonide (58) at 37°C in the liquid phase gave toluene, bibenzyl, phenylacetaldehyde, formic acid, (benzyloxymethyl)formate, and benzyl formate as products. In chlorinated solvents, benzyl chloride is also formed and in the presence of a radical quench such as 1-butanethiol, the product distribution changes. Electron spin resonance (ESR) signals are observed in the presence of spin traps, adding to the evidence that suggests radicals are involved in the decomposition mechanism (Scheme 9) <89JA5839>. 

Thermolysis of aryl chloro diazirine (18) in the presence of acetone and a trapping agent such as A -phenylmaleimide gave rise to cycloadducts such as 41. The unstable adduct hydrolyzed during purification resulting in synthesis of bicyclic hemiacetals 42 and 43 as a mixture of endo and exo adducts in 37 and 8% yield, respectively. The exclusive generation of the singlet carbene was confirmed by low-temperature electron spin resonance (ESR) study of the irradiated diazirine. 

One of the standardized methods, electron spin resonance (ESR) technique, permits identification of food that contains a hard, dry matrix, e.g., bone. When food containing bone is irradiated, free radicals are produced and trapped in the crystal lattice of the bone, which can be detected by ESR spectroscopy [137]. Thermoluminescence of contaminating minerals for detection of radiation treatment of, e.g., spices and dried fruits can be successfully applied [138, 139]. Another standardized method that has been developed for identification of irradiated fat-containing foods is the mass-spectrometric detection of radiation-induced 2-alkylcyclobutanones after gas-chromatographic separation [140]. The... 

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