Electron spin resonance studies free radicals

Electron Spin Resonance. Trapped free radicals in irradiated starch were studied utilizing an electron paramagnetic resonance instrument (Varian Associates Type 4500) fitted with a 100-kc. field modulation, Hi-lo power microwave bridge, and a multipurpose specimen cavity. The instrument is stated to have an accuracy of 10% and a minimum resolution of about lO spins per cc. Variants 0.1% pitch mixed with potassium chloride calibration standard containing 10 " spins per cm. of length was used as the reference curve. Samples and standard were contained in quartz tubes, 4 mm. in i.d., in sufficient depth to fill the cavity. 

Electron donor-acceptor complexes, electron transfer in the thermal and photochemical activation of, in organic and organometallic reactions, 29, 185 Electron spin resonance, identification of organic free radicals, 1, 284 Electron spin resonance, studies of short-lived organic radicals, 5, 23 Electron storage and transfer in organic redox systems with multiple electrophores, 28, 1... 

Radiation techniques, application to the study of organic radicals, 12, 223 Radical addition reactions, gas-phase, directive effects in, 16, 51 Radicals, cation in solution, formation, properties and reactions of, 13, 155 Radicals, organic application of radiation techniques, 12,223 Radicals, organic cation, in solution kinetics and mechanisms of reaction of, 20, 55 Radicals, organic free, identification by electron spin resonance, 1,284 Radicals, short-lived organic, electron spin resonance studies of, 5, 53 Rates and mechanisms of solvolytic reactions, medium effects on, 14, 1 Reaction kinetics, polarography and, 5, 1... 

The types and reactions postulated for reactive intermediates in the radiation chemistry of polyethylene are reviewed. Ultraviolet spectroscopy is an important tool in complementing data obtained from electron spin resonance studies. Finally, the kinetics of growth and decay of the allyl and polyenyl free radicals as inferred from ultraviolet spectra are discussed. 

The design temperature of 600°C. was chosen by considering coal as a free radical source. Electron spin resonance studies of coals (I) indicate that a rather sharp maximum in nonspin-paired electron content occurs in coals when processed in this temperature zone—i.e., 500°-550°C. Chlorine moreover can be converted to atomic chlorine by several energy sources—corona discharge, silent electric discharge, ca. 4700 A. light, etc. 

C. The same pattern holds for the data on ammonia yields, as one would expect from Equations 1 and 2. The increase at — 80°C. suggests an effect of phase change while the opposed temperature effect at — 196°C. suggests that a different reaction mechanism is controlling at — 196°C. consistent with observations from electron spin resonance studies that different stable-free radicals are observed below — 150°C. for glycine. The low carbonyl yields found for methionine and the peptides at — 80°C. indicate that the low temperature radicals may still be the stable forms at... 

Differences owing to warming rate are also to be expected on the basis of electron spin resonance studies (37) of protein and peptide systems which indicate that the free radicals observed on — 196°C. irradiation differ from those observed on room temperature irradiation and that the types observed at — 196°C. are transformed to the form observed at room temperature on wanning. Since some of the low temperature free radicals have half-lives of the order of days at — 196°C., long holding times and/or slow... 

The data support evidence from electron spin resonance studies by Henriksen 22,23,24,25) and Gordy 16) showing that the radicals present in irradiated proteins at —80° to — 196°C. are different from those found on room temperature irradiation. They found that the free radicals produced at — 196°C. are relatively stable at that temperature, but on warming to room temperature these free radicals both react with each other and... 

Das S, von Sonntag C (1986) Oxidation of trimethylamine by OH radicals in aqueous solution, as studied by pulse radiolysis, ESR and product analysis. The reactions of the alkylamine radical cation, the aminoalkyl radical and the protonated aminoalkyl radical. Z Naturforsch 41b 505-513 Dixon WT, Norman ROC, Buley AL (1964) Electron spin resonance studies of oxidation. Part II. Aliphatic acids and substituted acids. J Chem Soc 3625-3634 Draper HH, Squires EJ, Mahmoodi H, Wu J, Agarwal S, Hadley M (1993) A comparative evaluation of thiobarbituric acid methods for the determination of malondialdehyde in biological materials. Free Rad Biol Med 15 353-363... 

Huttermann J, Ward JF, Myers LS Jr (1971) Electron spin resonance studies of free radicals in irradiated single crystals of 5-methylcytosine. Int J Radiat PhysChem 3 117-129 Huttermann J, Ohlmann J, Schaefer A, Gatzweiler W (1991) The polymorphism of a cytosine anion studied by electron paramagnetic resonance spectroscopy. Int J Radiat Biol 59 1297-1311 Hwang CT, Stumpf CL, Yu Y-Q, Kentamaa HI (1999) Intrinsic acidity and redox properties of the adenine radical cation. Int J Mass Spectrom 182/183 253-259 Ide H, Otsuki N, Nishimoto S, Kagiya T (1985) Photoreduction of thymine glycol sensitized by aromatic amines in aqueous solution. J Chem Soc Perkin Trans 2 1387-1392 Idris Ali KM, Scholes G (1980) Analysis of radiolysis products of aqueous uracil + N20 solutions. J Chem Soc Faraday Trans 176 449-456... 

Schuchmann MN, Naumov S, Schuchmann H-P, von Sonntag J, von Sonntag C (2005) 4-Amino-3Ff-pyrimidin-2-one ("isocytosine") is a short-lived non-radical intermediate formed in the pulse radiolysis of cytosine in aqueous solution. Radiat Phys Chem 72 243-250 Schulte-Frohlinde D, Hildenbrand K (1989) Electron spin resonance studies of the reactions of OH and SO4 radicals with DNA, polynucleotides and single base model compounds. In Minisci F (ed) Free radicals in synthesis and biology. Kluwer, Dordrecht, pp 335-359 Schulte-Frohlinde D, Behrens G, Onal A (1986) Lifetime of peroxyl radicals of poly(U), poly(A) and single- and double-stranded DNA and the rate of their reaction with thiols. Int J Radiat Biol 50 103-110... 

Although the results of electron-spin resonance studies of alkyl substituted radicals and radical-ions are of great significance to the study of hyperconjugation (Symons, 1962), it seems that little attention has been paid to the results by workers primarily concerned with hyperconjugation rather than with free radicals. Thus in a recent conference on hyperconjugation (Tetrahedron, 1959) references to electron-spin resonance results were notable by their complete absence. 

Radicals, organic free, identification by electron spin resonance, 1, 284 Radicals, short-lived organic, electron spin resonance studies of, 5, 53 Reaction kinetics, polarography and, 5, 1... 

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