Hydrogen abstraction by thiyl radicals

Pryor, William A.; Gojon, Gabriel; Stanley, J. P.

doi:10.1021/ja00784a064

Cited by 15 publications

(10 citation statements)

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“…The reported "better" correlation with o+ have also been challenged on the grounds that most of these reactions give better, or at least as good, correlation with o-. We also find in the literature quite a few reports on the excellent correlations witho (20,21,23). Zavitsas and Pinto's (22) proposition has been refuted by the exponents of the polar effect theory on the grounds that the observed linear correlation between p and AH for only five radicals (Bra, CI,C-, CI., t-BuO., .C6H5) could be fortuitous and a reported positive p value by Pryor et al (21) should be impossible according to Zavitsas's treatment.…”

Section: (B) Hydrogen Abstraction Reactionssupporting

confidence: 61%

“…The results show that the apparent polar effect of substituents as stipulated by Howard and Chenier (l5c) and Pryor et al (21) can result from the resonance interaction of electronwithdrawing and electron-donating substituents with n-electrons of the aromatic ring.…”

Section: (B) Hydrogen Abstraction Reactionsmentioning

confidence: 58%

“…A common feature in all these correlations, till recently, has been a negative value for the reaction parameter p. Since all the reactions studied were with electrophilic radicals, a negative p suggests that structure I1 is more important than 111. Recently, however, Pryor et al (21) have, for the first time, reported a positive p value for the reaction of tertbutyl radicals with toluenes, which indicated a greater contribution of structure 111 to the transition state. A better correlation of these reactions with o+ rather than o has also been advanced as additional evidence to prove charge separation in the transition state.…”

Section: (B) Hydrogen Abstraction Reactionsmentioning

confidence: 99%

“…The applicability of Hammett p correlation in free radical abstraction of hydrogen from substituted toluenes has been one of the reasons for the formulation of the theory of polar effects in these reactions (13-15, 21,22). The course of these reactions is described as follows:…”

Section: (B) Hydrogen Abstraction Reactionsmentioning

confidence: 99%

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Substituent effects in some autoxidation and hydrogen abstraction reactions in terms of their field (F) and resonance (R) components inclusive of unique positional weighting factors

Patnaik¹,

Mallick²,

Rout³

et al. 1980

Can. J. Chem.

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Substituent effects in some autoxidation and hydrogen abstraction reactions have been studied in terms of the field (Fk) and resonance (Rk) components proposed by Swain and Lupton and the unique positional weighting factors fj and rj incorporated by Williams and Norrington with the aid of the following equation:[Formula: see text]where Pi's are the rate parameters, Pi0 being that for a standard reference compound. The correlations are found to be quite satisfactory, showing the general validity of the above equation for the types of reactions considered. From the information obtained from the present correlation studies, an attempt has been made to resolve the conflict with regard to the nature of the transition state involved in the hydrogen abstraction reactions – that is, whether or not there is charge separation in the transition state. The results of the present studies seem to suggest that both the differences in the resonance stabilization energies of the ring-substituted benzyl radical and the contribution of polar structures to the transition state are to be invoked to explain the observed data.

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Section: (B) Hydrogen Abstraction Reactionssupporting

confidence: 61%

Section: (B) Hydrogen Abstraction Reactionsmentioning

confidence: 58%

Section: (B) Hydrogen Abstraction Reactionsmentioning

confidence: 99%

Section: (B) Hydrogen Abstraction Reactionsmentioning

confidence: 99%

See 2 more Smart Citations

Substituent effects in some autoxidation and hydrogen abstraction reactions in terms of their field (F) and resonance (R) components inclusive of unique positional weighting factors

Patnaik¹,

Mallick²,

Rout³

et al. 1980

Can. J. Chem.

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“…The rates of reaction obtained (Table 1) are extremely high, particularly when compared with those rate constants published for hydrogen-atom abstractions from organic compounds by thiyl radicals, or of hydrogen-atom transfer from NADH (Walling & Rabinowitz, 1959;Pryor et al, 1973;Miyashita et al, 1977). For example, for the reaction:…”

Section: Gs + Nadh --Gs-+ Nadh + (25)mentioning

confidence: 62%

Thiyl and phenoxyl free radicals and NADH Direct observation of one-electron oxidation

Forni¹,

Willson²

1986

Biochemical Journal

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Absolute rate constants for the reaction of NADH with thiyl free radicals derived from various sulphurcontaining compounds of biological significance were measured by using the technique of pulse radiolysis. These and related reactions with phenoxyl free radicals are believed to occur through one-electron-transfer processes. Further evidence comes from studies with deuterated NADH. The results support the possibility that, in biochemical systems, thiols may act as catalysts linking hydrogen-atom and electron-transfer reactions.

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