Hydrogen abstraction by thiyl radicals

1973 ◽  
Vol 95 (3) ◽  
pp. 945-946 ◽  
Author(s):  
William A. Pryor ◽  
G. Gojon ◽  
J. P. Stanley
Keyword(s):  
Hydrogen Abstraction ◽  
Thiyl Radicals

Kinetics of One-Electron Oxidation of Thiols and Hydrogen Abstraction by Thiyl Radicals from .alpha.-Amino C-H Bonds

1994 ◽  
Vol 116 (26) ◽  
pp. 12010-12015 ◽  
Author(s):  
Rong Zhao ◽  
Johan Lind ◽  
Gabor Merenyi ◽  
Trygve E. Eriksen
Keyword(s):  
Hydrogen Abstraction ◽  
Thiyl Radicals ◽  
Kinetics Of

Intermediates in the photolysis of alkyl sulfides and disulfides in dilute glass matrices

1977 ◽  
Vol 55 (9) ◽  
pp. 1546-1557 ◽  
Author(s):  
Frank C. Adam ◽  
Allen John Elliot
Keyword(s):  
Bond Cleavage ◽  
Hydrogen Abstraction ◽  
Spectral Characteristics ◽  
Bond Rupture ◽  
Epr Spectrum ◽  
Radical Pairs ◽  
Thiyl Radicals ◽  
The Matrix ◽  
Solvent Molecules ◽  
Glass Matrices

Simple alkyl sulfides and disulfides have been photolysed at 253.7 nm in dilute rigid glasses of 3-methylpentane, and the reactions which occur both at 77 K and in the glass at higher temperatures have been studied using epr and optical spectroscopy. The end products of photolysis have been determined using glc at room temperature. In sulfides, C—S bond cleavage leads to 'hot' radical pairs that react with each other giving rise to the main diamagnetic products observed, or react with nearby solvent molecules in the matrix by hydrogen abstraction yielding RSH and the solvent derived radicals (M•) which dominate the initial epr spectrum at 77 K. Thiyl radicals (RS•) are produced in significant amounts only after the sulfide glasses have been warmed slightly to allow the cage reaction,[Formula: see text]to occur. Pethiyl radicals (RS2•) are not ordinarily observed in sulfide photolyses. Photolysis of disulfide-containing glasses gives rise to S—S bond rupture and mainly diamagnetic products, or to C—S bond cleavage resulting in the formation of solvent radicals and RS2. Very little RS• is generated on warming the matrices. As with ethyl mercaptan photolysis, radicals corresponding to α-hydrogen abstraction of the substrate are obtained for both ethyl sulfide and disulfide. The spectral characteristics and photolytic behaviour of the sulfur containing radical species have been investigated where possible.

Thiyl radicals in biological systems: significant or trivial?

1995 ◽  
Vol 61 ◽  
pp. 55-63 ◽  
Author(s):  
B. Kalyanaraman
Keyword(s):  
Mammalian Cells ◽  
Hydrogen Abstraction ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Oxidative Modification ◽  
Addition Reactions ◽  
Thiyl Radicals ◽  
Protein Thiols ◽  
Spin Resonance

Thiyl radicals are formed from one-electron oxidation of thiols. Thiyl radicals participate in a number of reactions including electron transfer, hydrogen abstraction and addition reactions with several biological constituents and xenobiotics. Thiyl radicals can be detected by optical spectroscopy or by electron spin resonance (ESR) spectroscopy. Thiyl radicals appear to play a role in the nitrosylation of thiols and protein thiols. The exact mechanism of thiol-induced enhancement of oxidative modification of low-density lipoprotein remains questionable. The proposed role of thiyl radicals in lipid peroxidation needs to be re-examined. It has been proposed that thiyl radicals are detoxified by superoxide dismutase in mammalian cells and by a thiol-specific enzyme in bacterial systems. We propose that thiols or protein thiols act as potent antioxidants in radical-induced damage via formation of thiyl radicals.

Reactions of alkyl free radicals with 4-vinylcyclohexene

1968 ◽  
Vol 46 (24) ◽  
pp. 3833-3839 ◽  
Author(s):  
J. Reid. Shelton ◽  
Earl E. Borchert
Keyword(s):  
Free Radicals ◽  
Hydrogen Abstraction ◽  
Product Distribution ◽  
Effect Of Temperature ◽  
Coupling Reactions ◽  
Peroxy Radicals ◽  
Alkyl Radicals ◽  
Thiyl Radicals ◽  
Dissociation Energies ◽  
Tertiary Alkyl

Tertiary alkyl and cyanoalkyl free radicals prepared from t-butyl peroxypivalate and azobisisobutyronitrile were reacted with 4-vinylcyclohexene (1) for comparison with results previously obtained in the reaction of certain alkyl, alkoxy, peroxy, and thiyl radicals with this model olefin. The (CH3)3C• and (CH3)2(CN)C• radicals (like thiyl but in contrast to t-butoxy and t-butyl peroxy radicals) added to the vinyl double bond with subsequent abstraction of hydrogen by the resulting secondary alkyl radicals to give RH adducts along with higher molecular weight material.Vinylcyclohexenyl radicals formed by hydrogen abstraction from 1 reacted mainly by coupling to form dehydro dimers. They also formed substituted products by coupling with cyanoisopropyl radicals, but not with t-butyl radicals. The presence of both stabilized and unstabilized alkyl radicals of both secondary and tertiary types in these reactions with 1 permitted the observation of differences in the relative tendencies of these types of radicals to participate in addition, hydrogen abstraction, disproportionation, and coupling reactions. The observed effect of temperature (60 and 90°) on product distribution, together with estimated bond dissociation energies, suggest that the addition of cyanoisopropyl radicals to 1 is a reversible process.

.beta.-Hydrogen abstraction by thiyl radicals

1992 ◽  
Vol 11 (10) ◽  
pp. 3165-3166 ◽  
Author(s):  
P. Huston ◽  
J. H. Espenson ◽  
A. Bakac
Keyword(s):  
Hydrogen Abstraction ◽  
Thiyl Radicals

A Reinvestigation of the Deceptively Simple Reaction of Toluene with ●OH, and the Fate of the Benzyl Radical. I. a Combined Thermodynamic and Kinetic Study on the Competition Between ●OH Addition and Hydrogen Abstraction Reactions.

2019 ◽  
Author(s):  
Zoi Salta ◽  
Agnie M. Kosmas ◽  
Marc E. Segovia ◽  
Martina Kieninger ◽  
Oscar Ventura ◽  
...  
Keyword(s):  
Density Functional ◽  
Room Temperature ◽  
Hydrogen Abstraction ◽  
Reaction Rates ◽  
Composite Model ◽  
Alternative Mechanism ◽  
Radical Intermediate ◽  
Experimental Conditions ◽  
Methyl Group ◽  
Benzyl Radical

This work reports density functional and composite model chemistry calculations performed on the reactions of toluene with the hydroxyl radical. Both experimentally observed H-abstraction from the methyl group and possible additions to the phenyl ring were investigated. Reaction enthalpies and heights of the barriers suggest that H-abstraction is more favorable than ●OH addition to the ring. The calculated reaction rates at room temperature and the radical-intermediate product fractions support this view. This is somehow contradictory with the fact that, under most experimental conditions, cresols are observed in a larger concentration than benzaldehyde. Since the accepted mechanism for benzaldehyde formation involves H-abstraction, a contradiction arises that begs for an explanation. In this first part of our work we give the evidences that support the preference of hydrogen abstraction over ●OH addition and suggest an alternative mechanism which shows that cresols can actually arise also from the former reaction and not only from the latter.

A Reinvestigation of the Deceptively Simple Reaction of Toluene with ●OH, and the Fate of the Benzyl Radical. I. a Combined Thermodynamic and Kinetic Study on the Competition Between ●OH Addition and Hydrogen Abstraction Reactions.

2019 ◽  
Author(s):  
Zoi Salta ◽  
Agnie M. Kosmas ◽  
Marc E. Segovia ◽  
Martina Kieninger ◽  
Oscar Ventura ◽  
...  
Keyword(s):  
Density Functional ◽  
Room Temperature ◽  
Hydrogen Abstraction ◽  
Reaction Rates ◽  
Composite Model ◽  
Alternative Mechanism ◽  
Radical Intermediate ◽  
Experimental Conditions ◽  
Methyl Group ◽  
Benzyl Radical

This work reports density functional and composite model chemistry calculations performed on the reactions of toluene with the hydroxyl radical. Both experimentally observed H-abstraction from the methyl group and possible additions to the phenyl ring were investigated. Reaction enthalpies and heights of the barriers suggest that H-abstraction is more favorable than ●OH addition to the ring. The calculated reaction rates at room temperature and the radical-intermediate product fractions support this view. This is somehow contradictory with the fact that, under most experimental conditions, cresols are observed in a larger concentration than benzaldehyde. Since the accepted mechanism for benzaldehyde formation involves H-abstraction, a contradiction arises that begs for an explanation. In this first part of our work we give the evidences that support the preference of hydrogen abstraction over ●OH addition and suggest an alternative mechanism which shows that cresols can actually arise also from the former reaction and not only from the latter.

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