Notes: Oxidation of Hindered Phenols. IX. Equilibria Between Phenoxy Radicals

1959 ◽  
Vol 24 (9) ◽  
pp. 1356-1358 ◽  
Author(s):  
Clinton Cook ◽  
Corrine Depatie ◽  
Edwin English
Keyword(s):  
Hindered Phenols ◽  
Phenoxy Radicals

Oxidation of Hindered Phenols. IV. Stable Phenoxy Radicals

1956 ◽  
Vol 78 (9) ◽  
pp. 2002-2005 ◽  
Author(s):  
Clinton D. Cook ◽  
David A. Kuhn ◽  
Peter Fianu
Keyword(s):  
Hindered Phenols ◽  
Phenoxy Radicals

Reactivity of Peroxy Radicals Coordinated to Vitamin B12 Studied by Electron Spin Resonance Spectroscopy

2004 ◽  
Vol 69 (11) ◽  
pp. 2091-2097 ◽  
Author(s):  
Alexander Tkáč ◽  
Eva Hanušovská
Keyword(s):  
Peroxy Radical ◽  
Resonance Spectroscopy ◽  
Vitamin B ◽  
Sterically Hindered Phenols ◽  
Peroxy Radicals ◽  
Oh Groups ◽  
Biological Targets ◽  
Hindered Phenols ◽  
Phenoxy Radicals ◽  
Radical Attack

One-electron transfer from chelated Co(II)(3d7) of vitamin B12 (cyanocobalamine) to tert-butylhydroperoxide forms at ambient temperature in non-polar solvents peroxy radicals stabilized by π-coordination to Co(III)(3d6) of the oxidized vitamin. In the absence of oxygen, the peroxy radicals manifest themselves as singlet ESR lines at g = 2.0174. After addition of sterically hindered phenols, apart from the decreased original singlet line, a new signal of stable phenoxy radicals, formed by H-abstraction from the phenols, is observed. Phenoxy radicals generated from unhindered phenols remain stabilized by σ-coordination to the cobalt(III) centre, giving rise to an ESR signal split into eight lines due to interaction of the unpaired electron with the magnetic moment of the 59Co nucleus (I = 7/2) of vitamin B12. Large molecules with unhindered OH groups, such as testosterone or cholesterol cannot be coordinated after the primary radical attack and the generated radicals disappear by recombination. By this technique, the sensitivity of biological targets to primary peroxy radical attack as well as the efficiency of different antioxidants (vitamin E, Stobadine) can be tested.

Research changes in the properties of butadiene-nitrile rubber under various aging conditions

2021 ◽  
pp. 009524432110290
Author(s):  
Mariya L Davydova ◽  
Aytalina F Fedorova
Keyword(s):  
Accelerated Aging ◽  
Physical And Mechanical Properties ◽  
Exposure Period ◽  
Climatic Conditions ◽  
Nitrile Rubber ◽  
Sterically Hindered Phenols ◽  
Loading Mode ◽  
Hindered Phenols ◽  
The Republic ◽  
Butadiene Nitrile Rubber

This article represents the results of a study of changes in the properties of vulcanizates based on BNR-18 butadiene-nitrile rubber containing as stabilizers the experimental spatially hindered phenols Stafen, CO3, CO4, and industrial antioxidant 6PPD, after accelerated aging (100°C 96 h) and aging under full-scale exposure in extreme climatic conditions of the Republic of Sakha (Yakutia) during 2 years. In winter, the air temperature reached—48°C, in summer—+36.1°C. It is shown that the experimental sterically hindered phenols more effectively under natural exposure conditions. They are characterized by the most stability in terms of strength throughout the entire exposure period. Under conditions of accelerated aging, the vulcanizate containing the industrial antioxidant 6PPD is characterized by the greatest stability of physical and mechanical properties. According to the viscoelastic characteristics obtained in the dynamic loading mode, the contribution of the presented stabilizers in maintaining resistance to temperature and deformation effects compared with unstabilized rubber is confirmed.

Studies on hindered phenols and analogs. 2. 1,3-Benzoxathioles having SRS-A inhibiting activity

1990 ◽  
Vol 33 (5) ◽  
pp. 1491-1496 ◽  
Author(s):  
Yuichi Aizawa ◽  
Tsutomu Kanai ◽  
Kazuo Hasegawa ◽  
Takeshi Yamaguchi ◽  
Yoshio Iizuka ◽  
...  
Keyword(s):  
Inhibiting Activity ◽  
Hindered Phenols
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