NMR and ESR of sulphenic acids and their derivatives

Protein thiyl radicals in disordered systems: A comparative EPR study at low temperature

“…32 Characteristic g-tensor values of disulfide radicals (perthiyl, disulfide anions and cations) as well as sulfoxyl radicals (sulfinyl, sulfonyl, thiyl peroxyl) are well established in low molecular weight thiols. 36,41 In our system with protein-based thiyl radicals generated photochemically at 77 K analogous temperature-dependent reactions have been observed. Traces of oxygen in the frozen matrix can react primarily with thiyl radicals forming sulfinyl radicals (R-CH 2 -S=O).…”

“…40 Sulfur-centered radicals with two or more s-bonded groups at the sulfur, as disulfide radicals (perthiyl, disulfide anion and cation), or sulfoxyl radicals (sulfinyl, sulfonyl, thiyl peroxyl) deviate distinctly from the axial molecular symmetry of thiyl radicals, and do not exhibit the exceptional spectroscopic properties of alkyl thiyl radicals; they are all well observable by EPR. 36,41 Most of our knowledge of the electronic structure of alkyl thiyl radicals originates from single crystal EPR data at low temperature on oriented radicals in several irradiated low molecular weight thiols. [22][23][24][25][26][27][28][29] For an interpretation of thiyl radical data in disordered systems, it is valuable to discuss briefly these crystal data (g-tensor, hyperfine tensors of the b-protons) which are summarized in Table 4.…”

“…38 Perthiyl radicals, also in proteins, have been known for a long time and are well described. 36,69 EPR data on protein-based perthiyl radicals, sulfinyl, sulfonyl, and thiyl peroxyl radicals are summarized in Table 1; their g-tensors are comparable with those of low molecular weight thiols. 30,31,33…”

Disulfide anion radical equilibria: effects of -NH3+, -CO2−, -NHC(O)- and -CH3 groups

“…Studies of low molecular weight disulfide anion radicals by electron spin resonance and theoretical methods have shown that the extra electron resides in a σ* bond between the two sulfur atoms and the overall bonding is σ(2)σ*(1). [7][8][9][10][11] By convention the three dot symbol in the above formula is used to indicate this. 12 The associated negative charge is indicated here by the superscript minus sign.…”

“RS+” as a Coupling Reagent for Phosphorylation and Carboxylic Acid Activation

“…[12] It has been reported, for example, that disulfide radical cations may be used in electrophilic aromatic substitutions. [13] These reagents are probably preferable to sulfenyl halides for carboxylate and phosphate activation in laboratory preparations, and studies in this direction are in progress.…”