Oxyhalogen–Sulfur Chemistry: Oxidation of a Thiourea Dimer, Formamidine Disulfide, by Chlorine Dioxide

2013 ◽  
Vol 66 (3) ◽  
pp. 362 ◽  
Author(s):  
Bice S. Martincigh ◽  
Morgen Mhike ◽  
Kayode Morakinyo ◽  
Risikat Ajibola Adigun ◽  
Reuben H. Simoyi
Keyword(s):  
Chlorine Dioxide ◽  
Sulfonic Acid ◽  
Stoichiometric Ratio ◽  
Sulfinic Acid ◽  
Sulfenic Acid ◽  
Acidic Media ◽  
Sulfur Chemistry ◽  
Spectrometric Data ◽  
Oxidative Pathway ◽  
Formamidine Disulfide

The oxidation of formamidine disulfide, FDS, the dimer of thiourea, by aqueous chlorine dioxide has been studied in highly acidic and mildly acidic media. FDS is one of the possible oxidation intermediates formed in the oxidation of thiourea by oxyhalogens to urea and sulfate. The reaction is exceedingly slow, giving urea and sulfate with a stoichiometric ratio of 5 : 14 FDS to chlorine dioxide after an incubation period of up to 72 h and only in highly acidic media which discourages the disproportionation of chlorine dioxide to the oxidatively inert chlorate. Mass spectrometric data suggest that the oxidative pathway proceeds predominantly through the sulfinic acid, proceeding next to the products sulfate and urea, while by-passing the sulfonic acid. Transient formation of the unstable sulfenic acid was also not observed.

Oxyhalogen–Sulfur Chemistry: Kinetics and Mechanism of Oxidation of Tiopronin by Acidified Bromate and Aqueous Bromine

2015 ◽  
Vol 68 (2) ◽  
pp. 262 ◽  
Author(s):  
Wilbes Mbiya ◽  
Risikat Adigun ◽  
Thai Tran ◽  
Yadana Htwe ◽  
Reuben H. Simoyi
Keyword(s):  
Reaction Network ◽  
Clinical Applications ◽  
Free Radical Scavenger ◽  
Radical Scavenger ◽  
Direct Reaction ◽  
Sulfinic Acid ◽  
Sulfenic Acid ◽  
Sulfur Chemistry ◽  
Thiyl Radicals ◽  
Wide Range

N-2-(Mercaptopropionyl)glycine (MPG) is a free-radical scavenger, a detoxicating synthetic aminothiol which also acts as an antioxidant with a wide range of clinical applications. The oxidation of MPG by aqueous bromine and acidified bromate has been studied by spectrophotometric techniques. The stoichiometry for the reaction of acidic bromate with MPG is 1 : 1, HS(CH3)CH(=O)N(H)CH2COOH + BrO3– → HO3S(CH3)CH(=O)N(H)CH2COOH + Br–, with reaction occurring only at the thiol centre. The involvement of thiyl radicals in the oxidation of MPG competes with a non-radical pathway involving two-electron oxidations of the sulfur centre. A bimolecular rate constant of 5.68 (±0.94) × 103 M–1 s–1 for the direct reaction of MPG with bromine was determined. Electrospray ionization spectral data show that MPG is oxidized through its sulfinic acid, by-passing the unstable sulfenic acid. A simplified reaction network consisting of 19 reactions was simulated and it gave a very good fit to the experimental data.

Kinetics and Mechanism of Oxidation of d-Penicillamine in Acidified Bromate and Aqueous Bromine

2016 ◽  
Vol 69 (11) ◽  
pp. 1305 ◽  
Author(s):  
Kudzanai Chipiso ◽  
Reuben H. Simoyi
Keyword(s):  
Sulfonic Acid ◽  
Biologically Active ◽  
Stopped Flow ◽  
Sulfinic Acid ◽  
Sulfenic Acid ◽  
Dimer Formation ◽  
Acid Product ◽  
Diffusion Controlled ◽  
Sulfinic Acids ◽  
Mechanism Of Oxidation

The oxidation of the biologically active compound d-penicillamine (Depen) by acidic bromate has been studied. The stoichiometry of the reaction is strictly 1 : 1, in which Depen is oxidized only as far as the sulfonic acid with no cleavage of the C–S bond to yield sulfate. Electrospray ionization spectroscopy shows that Depen is oxidized through addition of oxygen atoms on the sulfur centre to successively yield sulfenic and sulfinic acids before the product sulfonic acid. In conditions of excess Depen over the oxidant, sulfenic acid was not observed. Instead, nearly quantitative formation of the dimer was obtained. The dimer, which is the d-penicillamine disulfide species, was formed from a reaction of the putative highly electrophilic sulfenic acid with unreacted Depen in a condensation-type reaction and not through a radical-mediated pathway. Further oxidation of the dimer is slow because it is the most stable intermediate in the oxidation of Depen. In excess oxidant conditions, negligible dimer formation is observed. The reaction of bromine with Depen gives a stoichiometry of 3 : 1 with the same sulfonic acid product. This reaction is so fast that it is essentially diffusion controlled. Our stopped-flow instrument could not capture the oxidation by the first 2 moles of bromine, only the section of the reaction in which the sulfinic acid is oxidized to sulfonic acid.

Design of Ionic Liquid 3-Methyl-1-sulfonic Acid Imidazolium Nitrate as Reagent for the Nitration of Aromatic Compounds by in Situ Generation of NO2 in Acidic Media

2012 ◽  
Vol 77 (7) ◽  
pp. 3640-3645 ◽  
Author(s):  
Mohammad A. Zolfigol ◽  
Ardeshir Khazaei ◽  
Ahmad R. Moosavi-Zare ◽  
Abdolkarim Zare ◽  
Hendrik G. Kruger ◽  
...  
Keyword(s):  
Ionic Liquid ◽  
Aromatic Compounds ◽  
Sulfonic Acid ◽  
Acidic Media ◽  
In Situ Generation

ChemInform Abstract: DIRECT CONVERSION OF SULFINIC ACID TO SULFONIC ACID DERIVATIVES

1981 ◽  
Vol 12 (34) ◽  
Author(s):  
M. FURUKAWA ◽  
M. NISHIKAWA ◽  
Y. INABA ◽  
Y. NOGUCHI ◽  
T. OKAWARA ◽  
...  
Keyword(s):  
Sulfonic Acid ◽  
Direct Conversion ◽  
Sulfinic Acid

scholarly journals Sturucture of the stress response protein SAV1875 from S. aureus

2014 ◽  
Vol 70 (a1) ◽  
pp. C1509-C1509
Author(s):  
Hyojung Kim ◽  
Aeran Kwon ◽  
Bongjin Lee
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Stress Protein ◽  
Catalytic Triad ◽  
Sulfinic Acid ◽  
Sulfenic Acid ◽  
Large Protein ◽  
Core Domain ◽  
Disease Protein ◽  
Protein Group

The DJ-1/ThiJ/PfpI superfamily is a large protein group over diverse organisms, under this superfamily, there are multi-types of proteins such as protease, chaperones, heat shock protein, human parkinson's disease protein. The conserved protein from Staphylococcus aureus SAV1875 is a member of DJ-1 superfamily, but its function is unknown. We have determined the crystal structure of SAV1875 to a resolution of 1.8Å . As expected, the overall fold of the core domain of SAV1875 is similar to that of DJ-1. SAV1875 appears to be a dimer both in solution and the crystal, displaying an oligomerization interface similar to that observed for DJ-1. SAV 1875 contains a possible catalytic triad (Cys105-Glu17-His106) analogous to PfpI, YhbO, and DR1199. The cysteine in this triad (Cys-105) is oxidized in this crystal structure, similar to modifications seen in the cysteine of the DJ-1. This Cys-sulfenic acid is stabilized by hydrogen bonding with Glu17, Gly72, His106. We also have determined the crystal structure of mutated form of reactive Cys, SAV1875 C105D to a resolution of 2.1 Å. Aspartate mutation mimics the the Cys-sulfinic acid, more oxidized form. The aspartate stabilization by hydrogen bonding with neighboring residues are maintained. On the basis of these results, we suggest that SAV1875 might work as a general stress protein involved in the detoxification of the cell from oxygen reactive species.

Oxyhalogen–Sulfur Chemistry: Kinetics and Mechanism of Oxidation of N-Acetyl-ʟ-methionine by Aqueous Iodine and Acidified Iodate

2014 ◽  
Vol 67 (4) ◽  
pp. 626 ◽  
Author(s):  
Kudzanai Chipiso ◽  
Wilbes Mbiya ◽  
Moshood K. Morakinyo ◽  
Reuben H. Simoyi
Keyword(s):  
Methionine Sulfoxide ◽  
Kinetics And Mechanism ◽  
Ionization Mass ◽  
Stoichiometric Ratio ◽  
Inhibitory Effects ◽  
Electron Transfer Process ◽  
Sulfur Chemistry ◽  
Methionine Supplementation ◽  
Mechanism Of Oxidation ◽  
Sole Product

The use of N-acetyl-l-methionine (NAM) as a bio-available source for methionine supplementation as well as its ability to reduce the toxicity of acetaminophen poisoning has been reported. Its interaction with the complex physiological matrix, however, has not been thoroughly investigated. This manuscript reports on the kinetics and mechanism of oxidation of NAM by acidic iodate and aqueous iodine. Oxidation of NAM proceeds by a two electron transfer process resulting in formation of a sole product: N-acetyl-l-methionine sulfoxide (NAMS=O). Data from electrospray ionization mass spectrometry confirmed the product of oxidation as NAMS=O. The stoichiometry of the reaction was deduced to be IO3– + 3NAM → I– + 3NAMS=O. In excess iodate, the stoichiometry was deduced to be 2IO3– + 5NAM + 2H+ → I2 + 5NAMS=O + H2O. The reaction between aqueous iodine and NAM gave a 1 : 1 stoichiometric ratio: NAM + I2 + H2O → NAMS=O + 2I– + H+. This reaction was relatively rapid when compared with that between NAM and iodate. It did, however, exhibit some auto-inhibitory effects through the formation of triiodide (I3–) which is a relatively inert electrophile when compared with aqueous iodine. A simple mechanism containing 11 reactions gave a reasonably good fit to the experimental data.

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