Study of the mechanism of oxidation of polysulphide oligomers using sodium bichromate

Averko-Antonovich, L. A.; Rubanov, V.Ye.; Klimova, L.I.

doi:10.1016/0032-3950(77)90198-8

Cited by 2 publications

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“… , has focused on the industrial significance of Cr(VI) reduction, using smaller, non-biological thiols in non-aqueous solvents. The reaction of Cr(VI) with alkane- and arenethiols in N,N -dimethylformamide (DMF), as in aqueous solution, resulted in the oxidation of thiols to the corresponding disulfides and the reduction of Cr(VI) to Cr(III) . NMR, UV/vis, and IR studies revealed that the first step in the reduction of Cr(VI) by thiols in DMF involved the substitution of a thiolate, RS - , for the hydroxyl group in hydrogen chromate, HOCrO 3 - , and the formation of a Cr(VI)−thioester which was subsequently reduced by additional thiol. , Mazurek et al have synthesized and crystallized several Cr(VI)−thioesters of small alkyl and aryl thiols, and have structurally characterized tetraphenylarsonium ( p- bromophenyl)thiolato)chromate(VI), [Ph 4 As][ p- BrPhS−CrO 3 ], via X-ray crystallography …”

Section: Introductionmentioning

confidence: 99%

Chromium(VI) Forms Thiolate Complexes with γ-Glutamylcysteine, N-Acetylcysteine, Cysteine, and the Methyl Ester of N-Acetylcysteine

et al. 1996

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Reaction of potassium dichromate with gamma-glutamylcysteine, N-acetylcysteine, and cysteine in aqueous solution resulted in the formation of 1:1 complexes of Cr(VI) with the cysteinyl thiolate ligand. The brownish red Cr(VI)-amino acid/peptide complexes exhibited differential stability in aqueous solutions at 4 degrees C and ionic strength = 1.5 M, decreasing in stability in the order: gamma-glutamylcysteine > N-acetylcysteine > cysteine. (1)H, (13)C, and (17)O NMR studies showed that the amino acids act as monodentate ligands and bind to Cr(VI) through the cysteinyl thiolate group, forming RS-Cr(VI)O(3)(-) complexes. No evidence was obtained for involvement of any other possible ligating groups, e.g., amine or carboxylate, of the amino acid/peptide in binding to Cr(VI). EPR studies showed that chromium(V) species at g = 1.973-4 were formed upon reaction of potassium dichromate with gamma-glutamylcysteine and N-acetylcysteine. Reaction of potassium dichromate or sodium dichromate with N-acetylcysteine and the methyl ester of N-acetylcysteine in N,N-dimethylformamide (DMF) also led to the formation of RS-Cr(VI)O(3)(-) complexes as determined by UV/vis, IR, and (1)H NMR spectroscopy. Thus, an early step in the reaction of Cr(VI) with cysteine and cysteine derviatives in aqueous and DMF solutions involves the formation of RS-CrO(3)(-) complexes. The Cr(VI)-thiolate complexes are more stable in DMF than in aqueous solution, and their stability towards reduction in aqueous solution follows the order cysteine < N-acetylcysteine < gamma-glutamylcysteine < glutathione.

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