Electron Spin Resonance Study of Phenolic Antioxidants. II. Free Radical Structures Arising from Antioxidants Containing the 3,5-DI-Tert.-Butyl-4-Hydroxy-Benzyl Group

1973 ◽  
Vol 46 (5) ◽  
pp. 1134-1155 ◽  
Author(s):  
J. C. Westfahl
Keyword(s):  
Free Radicals ◽  
Electron Spin Resonance ◽  
Esr Spectroscopy ◽  
Quinone Methide ◽  
Electron Spin Resonance Study ◽  
Phenolic Antioxidants ◽  
Primary Radical ◽  
Tert Butyl ◽  
Spin Resonance ◽  
Spin Resonance Study

Abstract Oxidation of a series of phenolic antioxidants, or compounds related to antioxidants, was carried out using ferricyanide ion in dimethylsulfoxide solution. The free radicals produced were studied by ESR spectroscopy. Most of the antioxidants examined contained one or more 3,5-di-tert-butyl-4-hy-droxybenzyl groups. Based on their behavior on oxidation, the compounds can be divided into two classes. One class forms a relatively unstable primary radical which decomposes to give 2,6-di-tert-butyl quinone methide.

Electron Spin Resonance Study of Phenolic Antioxidants. Correlations of Organic Free Radical Stability with Antioxidant Activity

1972 ◽  
Vol 45 (2) ◽  
pp. 402-422 ◽  
Author(s):  
J. C. Westfahl ◽  
C. J. Carman ◽  
R. W. Layer
Keyword(s):  
Molecular Structure ◽  
Free Radicals ◽  
Electron Spin Resonance ◽  
Electron Spin ◽  
Esr Spectroscopy ◽  
Spectroscopic Technique ◽  
Electron Spin Resonance Study ◽  
Phenolic Antioxidants ◽  
Radical Concentration ◽  
Spin Resonance

Abstract Electron spin resonance (ESR) is a well established, sensitive spectroscopic technique for determining the molecular structure, as well as the lifetime or stability of organic free radicals. Consequently, ESR spectroscopy provides a logical method for gaining insight into the role that free radicals play in the stabilization of rubber by organic antioxidants. We used ESR spectroscopy to determine the molecular structure of the phenoxyl free radicals derived from a series of twelve phenolic antioxidants. We also used ESR to measure relative radical concentrations of the free radicals and evaluated the twelve phenolic antioxidants relative to each other. We have found that the ESR measurement of relative radical concentration is a measure of relative radical stability, and that the relative radical stability is temperature dependent. By plotting relative radical concentration (or stability) as a function of temperature, we can rank these twelve antioxidants relative to each other. This ranking is in good agreement with the activity of these antioxidants in EPDM. These data were discussed in relation to antioxidant mechanism.

Notizen: Synthesis and Electron Spin Resonance Study of Spin-Labelled Compounds Related to Tumour- Growth Inhibitory Nitroarylaziridines

1976 ◽  
Vol 31 (5-6) ◽  
pp. 328-330 ◽  
Author(s):  
N. Dodd ◽  
R. Harcus ◽  
P. Preston
Keyword(s):  
Free Radicals ◽  
Electron Spin Resonance ◽  
Electron Spin ◽  
Esr Spectroscopy ◽  
Tumour Growth ◽  
Electron Spin Resonance Study ◽  
Growth Inhibitory ◽  
Spin Resonance ◽  
Stable Free Radicals ◽  
Spin Resonance Study

Abstract Three stable free radicals have been prepared which are akin to 5-aziridino-2,4-dinitrobenzamide (CB 1954) ; these compounds all contain a nitroxide function. The metabolism and excretion of two such compounds in mice has been monitored by electron spin resonance (ESR) spectroscopy and compared with that of the simpler nitioxide, 4-keto-2,2,6,6-tetramethylpiperidino-1-oxyl (tempone).

An electron spin resonance study of ultraviolet photolyzed methanol adsorbed on porous high-silica glass

1969 ◽  
Vol 47 (8) ◽  
pp. 1375-1379 ◽  
Author(s):  
Michie Shimizu ◽  
H. D. Gesser ◽  
M. Fujimoto
Keyword(s):  
Free Radicals ◽  
Electron Spin Resonance ◽  
Electron Spin ◽  
Silica Glass ◽  
Electron Spin Resonance Study ◽  
Surface Contaminants ◽  
Spin Resonance ◽  
High Silica ◽  
Glass Surfaces ◽  
Spin Resonance Study

The electron spin resonance (e.s.r.) spectra of •CH3, •CHO, H and/or D, and possibly •CH2OH or •CH2OD were found by the ultraviolet (u.v.) photolysis of methanol —OH or —OD on porous high-silica glass at 77 °K. These e.s.r. spectra resemble the results of the u.v. photolysis of X-irradiated methanol indicating that some perturbation and/or sensitization occurred in the molecules by the glass surface. The absence of e.s.r. spectra from the same systems on the acid-leached glass, on the totally fluorinated glass, or on the totally —OH covered glass suggests that (i) the co-existence of surface contaminants, such as Al and Zr and not B, and some of surface —OH could be responsible for producing these free radicals, and (ii) the methanols adsorbed on these glass surfaces are stabilized against u.v. photolysis.

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