Sulfur Radical Cations

Glass, Richard S.

doi:10.1007/3-540-48986-x_1

Cited by 76 publications

(39 citation statements)

References 453 publications

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“…In a type I mechanism, the initially formed sulfide radical cation RSR • + can undergo different reactions: 28 (1) Addition of superoxide radical anion to give the same peroxysulfoxide A as in type II mechanism (Scheme 1, eqn. ( 6)) or, as proposed by Baciocchi, 15 one of its possible isomer.…”

Section: Discussionmentioning

confidence: 99%

Photo-oxidation of di-n-butylsulfide by various electron transfer sensitizers in oxygenated acetonitrile

Latour

Pigot

Simon

et al. 2005

Photochem Photobiol Sci

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The selective activation of different photosensitizers has been carried out under comparable conditions and their efficiency towards di-n-butylsulfide oxidation in oxygenated acetonitrile compared from the product distribution after 150 minutes of irradiation. As expected, the best selectivity towards sulfoxide is obtained with a conventional energy transfer sensitizer such as Rose Bengal (RB), but also with a quinone with a low-lying triplet state, 2,3,5,6-tetrachloro-1,4-benzoquinone (chloranil or CHLO) and with 9,10-dicyanoanthracene (DCA). More significant yields in sulfonic and sulfuric acids are obtained under sensitization with 9,10-anthraquinone (ANT) or a derivative of benzophenone, 4-benzoyl benzoic acid (4-BB), with which additional experiments were carried out in order to discuss the involvement of either singlet oxygen or superoxide radical anion. Triphenyl pyrylium tetrafluoroborate (TPT+) is inefficient under the selected conditions and sulfide photo-oxidation can only be achieved with higher TPT+ concentrations with simultaneous total TPT+ bleaching. With TPT+, 1,2,4,5-tetracyanobenzene (TCNB) and TiO2, the product distribution and the low selectivity as well as the formation of numerous common by-products are indicative of radical mechanisms. All these results are discussed according to the possible formation of activated oxygen species, such as singlet oxygen, superoxide radical anion or alkylperoxy radicals.

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Section: Discussionmentioning

confidence: 99%

Photo-oxidation of di-n-butylsulfide by various electron transfer sensitizers in oxygenated acetonitrile

Latour

Pigot

Simon

et al. 2005

Photochem Photobiol Sci

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“…A notable and dramatic example is merostabilization (i.e., the stabilization due to the simultaneous interaction of both electron-donating and electron-accepting substituents with the same radical center, also known as the captodative effect). , Furthermore, the partial delocalization of radical electrons to heteroatoms, down Mendeleev’s table, also tends to stabilize monoradicals. Sulfur, for example, has been used extensively in the design of persistent radicals. − The reactivity of radicals (and the ways of decreasing it, mentioned above) is widely utilized chemically as well as biologically. ,, …”

Section: Radical Reactivitymentioning

confidence: 99%

Do Diradicals Behave Like Radicals?

et al. 2019

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This review sets out to understand the reactivity of diradicals and how that may differ from monoradicals. In the first part of the review, we delineate the electronic structure of a diradical with its two degenerate or nearly degenerate molecular orbitals, occupied by two electrons. A classification of diradicals based on whether or not the two SOMOs can be located on different sites of the molecule is useful in determining the ground state spin. Important is a delocalized to localized orbital transformation that interchanges “closed-shell” to “open-shell” descriptions. The resulting duality is useful in understanding the dual reactivity of singlet diradicals. In the second part of the review, we examine, with a consistent level of theory, activation energies of prototypical radical reactions (dimerization, hydrogen abstraction, and addition to ethylene) for representative organic diradicals and diradicaloids in their two lowest spin states. Differences and similarities in reactivity of diradicals vs monoradicals, based on either a localized or delocalized view, whichever is suitable, are then discussed. The last part of this review begins with an extensive, comparative, and critical survey of available measures of diradical character and ends with an analysis of the consequences of diradical character for selected diradicaloids.

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“…However, these interesting observations need some comments and explanations. Since the main source of αS • is the α-deprotonation of S ●+ [ 26 ], it seems obvious that the deprotonation of S •+ to form αS(2) • is much faster for 2 than for 1 . As it was stated earlier [ 27 ], the efficiency of α-deprotonation strongly depends on the molecular structure of S •+ and, to be more specific, on the relative alignment of the singly occupied sulfur p-orbital with the C−H σ-bond to be cleaved.…”

Section: Resultsmentioning

confidence: 99%

Evaluation of Hydroxyl Radical Reactivity by Thioether Group Proximity in Model Peptide Backbone: Methionine versus S-Methyl-Cysteine

Chatgilialoglu

Grzelak

Skotnicki

et al. 2022

IJMS

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Hydroxyl radicals (HO•) have long been regarded as a major source of cellular damage. The reaction of HO• with methionine residues (Met) in peptides and proteins is a complex multistep process. Although the reaction mechanism has been intensively studied, some essential parts remain unsolved. In the present study we examined the reaction of HO• generated by ionizing radiation in aqueous solutions under anoxic conditions with two compounds representing the simplest model peptide backbone CH3C(O)NHCHXC(O)NHCH3, where X = CH2CH2SCH3 or CH2SCH3, i.e., the Met derivative in comparison with the cysteine-methylated derivative. We performed the identification and quantification of transient species by pulse radiolysis and final products by LC–MS and high-resolution MS/MS after γ-radiolysis. The results allowed us to draw for each compound a mechanistic scheme. The fate of the initial one-electron oxidation at the sulfur atom depends on its distance from the peptide backbone and involves transient species of five-membered and/or six-membered ring formations with different heteroatoms present in the backbone as well as quite different rates of deprotonation in forming α-(alkylthio)alkyl radicals.

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Sulfur Radical Cations

Cited by 76 publications

References 453 publications

Photo-oxidation of di-n-butylsulfide by various electron transfer sensitizers in oxygenated acetonitrile

Photo-oxidation of di-n-butylsulfide by various electron transfer sensitizers in oxygenated acetonitrile

Do Diradicals Behave Like Radicals?

Evaluation of Hydroxyl Radical Reactivity by Thioether Group Proximity in Model Peptide Backbone: Methionine versus S-Methyl-Cysteine

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