Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Kinetics electron spin resonance spectroscopy

Gregor, W. Grabner, G. Adelwohrer, C. Rosenau, T. Gille, L. Antioxidant properties of natural and synthetic chromanol derivatives study by fast kinetics and electron spin resonance spectroscopy. J. Org. Chem. 2005, 70(9), 3472-3483. [Pg.216]

It is true that in some cases, the spectroscopic data on a reactive intermediate are so persuasive that the connection between structure and spectroscopic features is firm. However, in general this will not be the case, and additional spectroscopic or preparative criteria will have to be provided. So we are faced with the question How can we connect the information obtained, for example, from observations in matrices or in solution-phase fast kinetic studies, to molecular structure How do we know that the results of these experiments, using what we hopefully call direct methods, really pertain to the species we are trying to characterize I attempt to deal with this issue in what follows. Since the methods used vary from one class of non-Kekule species to another, specific classes are individually discussed, and special techniques are introduced as needed. Electron spin resonance spectroscopy has played such a pervasive role that it will be useful to give first a brief outline of that method. [Pg.171]

Wardman P, Dennis MF, Everett SA, Patel KB, Stratford MRL, Tracy M (2003) Radicals from one-electron reduction of nitro compounds, aromatic N-oxides and quinones the kinetic basis for hypoxia-selective, bioreductive drugs. Biochem Soc Symp 61 171-194 Warman JM, de Haas MP, Hummel A, van Lith D, VerberneJB, Loman H (1980) A pulse radiolysis conductivity study of frozen aqueous solutions of DNA. Int J Radiat Biol 38 459-459 Warman JM, de Haas MP, Rupprecht A (1996) DNA a molecular wire Chem Phys Lett 249 319-322 Warters RL, Lyons BW (1992) Variation in radiation-induced formation of DNA double-strand breaks as a function of chromatin structure. Radiat Res 130 309-318 Warters RL, Hofer KG, Harris CR, Smith JM (1977) Radionuclide toxicity in cultured mammalian cells Elucidation of the primary site of radiation damage. Curr Top Radiat Res Q 12 389-407 Weiland B, Huttermann J (1998) Free radicals from X-irradiated, dry and hydrated lyophilized DNA as studies by electron spin resonance spectroscopy analysis of spectral components between 77 K and room temperature. Int J Radiat Biol 74 341-358 Weinfeld M, Soderlind K-JM (1991) 32P-Postlabeling detection of radiation-induced DNA-damage identification and estimation of thymine glycols and phosphoglycolate termini. Biochemistry 30 1091-1097... [Pg.480]

Poth M, Focht DD (1985) 15N kinetic analysis of N20 production by Nitrosomonas europaea an examination nitrifier denitrification. Appl Environ Microbiol 49 1134-1141 Powell SJ, Prosser JI (1985) The effect of nitrapyrin and chloropicolinic acid on ammonium oxidation by Nitrosomonas europaea. FEMS Microbiol Lett 28 51-54 Prince RC, Hooper AB (1987) Resolution of the hemes of hydroxylamine oxidoreductase by redox potentiometry and electron spin resonance spectroscopy. Biochemistry 26 970-974 Probst I, Bruschi M, Pfennig N, LeGall J (1977) Cytochrome c-551.5(c7) from Desulfuromonas acetoxidans. Biochim Biophys Acta 460 58-64... [Pg.143]

Kinetic Theory of Fracture. Catastrophic failure of a polymeric material is a complex process in which a sequence of partially understood events occurs at both the molecular and macroscopic levels. The stress-induced cleavage of the main-chain polymer bond is one event occurring on the molecular level which has been studied by both stress MS and electron spin resonance spectroscopy (ESR). [Pg.65]

Matsumoto A, Mizuta K. Detailed kinetic analysis of the radical polymerization of trans -tert-butylcyclohexyl methacrylate in benzene based on the rate constants determined by electron spin resonance spectroscopy. Macromolecules 1994 27 5863-5870. [Pg.225]

Malatesta, V. and Ingold, K.U., Kinetic apphcations of electron spin resonance spectroscopy, amin-ium radicals, /. Am. Chem. Soc., 95, 6400,1973. [Pg.2082]

PLP-SEC and (iii) single-pulse pulsed-laser polymerization coupled with online time-resolved electron-spin resonance spectroscopy (SP-PLP-EPR). The propagation rate coefficient for MCRs may be obtained via ft-PLP-SEC and SP-PLP-EPR. Termination rate coefficients kt , and kt are only accessible from SP-PLP-EPR," in which different types of radicals can simultaneously be traced as a function of time. Remaining kinetic coefficients can then be obtained via computer modeling. Table 1.5 collates kinetic coefficients for butyl acrylate polymerization as an example. [Pg.38]

The reaction of eq. 16.9 will regenerate the antioxidant Arj-OH at the expense of the antioxidant At2-OH. Despite the fact that such regeneration reactions are not simple electron transfer reactions, the rate of reactions like that of eq. 16.9 has been correlated with the E values for the respective Ar-0. Thermodynamic and kinetic effects have not been clearly separated for such hierarchies, but for a number of flavonoids the following pecking order was established in dimethyl formamid (DMF) by a combination of electrolysis for generating the a-tocopherol and the flavonoid phenoxyl radicals and electron spin resonance (ESR) spectroscopy for detection of these radicals (Jorgensen et al, 1999) ... [Pg.324]

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. [Pg.41]

Several factors have contributed to this goal in the recent past development of electrochemical techniques for the study of complex reactions at solid electrodes, use of physical methods such as ESCA, Auger, LEED, etc. for the study of surfaces in the ultrahigh vacuum (UHV) environment and in situ techniques under the same conditions as the electrode reaction. Ellipsometry, electroreflectance, Mossbauer, enhanced Raman, infrared, electron spin resonance (ESR) spectroscopies and measurement of surface resistance and local changes of pH at surfaces were incorporated to the study of electrode kinetics. [Pg.66]

If Ja has been determined and the concentration of X is known it is now possible to determine kt 5 [Rt-]. The classical problem confronting the kineticist now arises how can one obtain a useful quantitative measurement of the rate coefficient, kx s, so that it will be of value either to theoreticians or to persons interested in applying kinetic data to complex systems It must be remembered that, if Rt- radicals react sufficiently rapidly with X so that they may be considered to disappear right at the place where they are formed, it might be possible to use electron spin resonance, or in certain rare cases absorption spectroscopy, to determine [R ]. Suffice it to say that some measurement other than a purely kinetic one must be used if k13 is to be obtained with the system in question. If one value of k15 is known, values for other gases can be obtained since relative rate coefficients are easier to determine than absolute ones. [Pg.9]

Since the heroic early mechanistic investigations, there have been two developments of major significance in radical chemistry. The first was the advent of electron spin resonance (ESR) spectroscopy (and the associated technique of chemically induced dynamic nuclear polarisation, CIDNP) [24], which provided structural as well as kinetic information the second is the more recent development of a wide range of synthetically useful radical reactions [20]. Another recent development, the combination of the pulse radiolysis and laser-flash photolysis techniques, is enormously powerful for the study of radicals but beyond the scope of this book. [Pg.13]

Methods such as nuclear magnetic resonance (NMR), electron spectroscopy for chemical analysis (ESCA), electron spin resonance (ESR), infrared (IR), and laser raman spectroscopy could be used in conjunction with rate studies to define mechanisms. Another alternative would be to use fast kinetic techniques such as pressure-jump relaxation, electric field pulse, or stopped flow (Chapter 4), where chemical kinetics are measured and mechanisms can be definitively established. [Pg.17]

A convenient way to study the kinetics and the mechanisms of H atom reactions in solution is to generate them by the pulse radiolysis of aqueous solutions at a low pH. Acetamide radicals, CH2C(=0)NH2, were identified in the pulse radiolysis of aqueous solutions of a-(methylthioacetamide), H3C-S-CH2C(=0)NH2, by time-resolved electron spin resonance (TRESR) spectroscopy. Only three mechanisms seemed plausible for such an observation. The first possibility is a two-step mechanism with an H-abstraction [reaction (27)] ... [Pg.460]

From the analysis of the data in the LIPID AT database (41), more than 150 different methods and method modifications have been used to collect data related to the lipid phase transitions. Almost 90% of the data is accounted for by less than 10 methods. Differential scaiming calorimetry strongly dominates the field with two thirds of all phase transition records. From the other experimental techniques, various fluorescent methods account for 10% of the information records. X-ray diffraction, nuclear magnetic resonance (NMR), Raman spectroscopy, electron spin resonance (ESR), infrared (IR) spectroscopy, and polarizing microscopy each contribute to about or less than 2-3% of the phase transition data records in the database. Especially useful in gaining insight into the mechanism and kinetics of lipid phase transitions has been time-resolved synchrotron X-ray diffraction (62,78-81). [Pg.903]


See other pages where Kinetics electron spin resonance spectroscopy is mentioned: [Pg.434]    [Pg.187]    [Pg.1]    [Pg.434]    [Pg.187]    [Pg.1]    [Pg.163]    [Pg.40]    [Pg.68]    [Pg.163]    [Pg.260]    [Pg.366]    [Pg.34]    [Pg.222]    [Pg.210]    [Pg.71]    [Pg.6]    [Pg.103]    [Pg.450]    [Pg.225]    [Pg.9]    [Pg.9]    [Pg.140]    [Pg.140]    [Pg.262]    [Pg.198]    [Pg.135]    [Pg.31]    [Pg.44]    [Pg.256]    [Pg.279]    [Pg.387]    [Pg.577]   
See also in sourсe #XX -- [ Pg.171 ]




SEARCH



Electron kinetic

Electron kinetics

Electron spin spectroscopy

Electrons resonance spectroscopy

Kinetic electronic

Kinetic spectroscopy

SPECTROSCOPY SPINNING

Spectroscopy electron spin resonance

© 2024 chempedia.info