Reactions of coordinated imidazole. Oxidation products and ring cleavage in the reactions of RImH3+ (R = pentaamminecobalt) with acetyl hypobromite and hypobromous acid

1991 ◽  
Vol 30 (7) ◽  
pp. 1635-1642 ◽  
Author(s):  
Allan G. Blackman ◽  
David A. Buckingham ◽  
Charles R. Clark ◽  
Jim. Simpson
Keyword(s):  
Oxidation Products ◽  
Ring Cleavage ◽  
Hypobromous Acid

Substrates and products of eosinophil peroxidase

2001 ◽  
Vol 358 (1) ◽  
pp. 233-239 ◽  
Author(s):  
Christine J. van DALEN ◽  
Anthony J. KETTLE
Keyword(s):  
Hypochlorous Acid ◽  
Plasma Concentrations ◽  
Oxidation Products ◽  
Inflammatory Conditions ◽  
Eosinophil Peroxidase ◽  
Hypohalous Acids ◽  
Hypobromous Acid ◽  
Michaelis Constants ◽  
The One ◽  
Compound Ii

Eosinophil peroxidase has been implicated in promoting oxidative tissue damage in a variety of inflammatory conditions, including asthma. It uses H2O2 to oxidize chloride, bromide and thiocyanate to their respective hypohalous acids. The aim of this study was to establish which oxidants eosinophil peroxidase produces under physiological conditions. By measuring rates of H2O2 utilization by the enzyme at neutral pH, we determined the catalytic rate constants for bromide and thiocyanate as 248 and 223s−1 and the Michaelis constants as 0.5 and 0.15mM respectively. On the basis of these values thiocyanate is preferred 2.8-fold over bromide as a substrate for eosinophil peroxidase. Eosinophil peroxidase catalysed substantive oxidation of chloride only below pH6.5. We found that when eosinophil peroxidase or myeloperoxidase oxidized thiocyanate, another product besides hypothiocyanite was formed; it also converted methionine into methionine sulphoxide. During the oxidation of thiocyanate, the peroxidases were present as their compound II forms. Compound II did not form when GSH was included to scavenge hypothiocyanite. We propose that the unidentified oxidant was derived from a radical species produced by the one-electron oxidation of hypothiocyanite. We conclude that at plasma concentrations of bromide (20–120μM) and thiocyanate (20–100μM), hypobromous acid and oxidation products of thiocyanate are produced by eosinophil peroxidase. Hypochlorous acid is likely to be produced only when substrates preferred over chloride are depleted. Thiocyanate should be considered to augment peroxidase-mediated toxicity because these enzymes can convert relatively benign hypothiocyanite into a stronger oxidant.

scholarly journals Degradation of 2,4,6-Trichlorophenol by Phanerochaete chrysosporium: Involvement of Reductive Dechlorination

1998 ◽  
Vol 180 (19) ◽  
pp. 5159-5164 ◽  
Author(s):  
G. Vijay Bhasker Reddy ◽  
Maarten D. Sollewijn Gelpke ◽  
Michael H. Gold
Keyword(s):  
Phanerochaete Chrysosporium ◽  
Reductive Dechlorination ◽  
Oxidation Products ◽  
Ring Cleavage ◽  
Fungal Metabolites ◽  
Subsequent Degradation ◽  
Metabolic Conditions ◽  
The Common ◽  
Dechlorination Reaction

ABSTRACT Under secondary metabolic conditions, the lignin-degrading basidiomycete Phanerochaete chrysosporium mineralizes 2,4,6-trichlorophenol. The pathway for the degradation of 2,4,6-trichlorophenol has been elucidated by the characterization of fungal metabolites and oxidation products generated by purified lignin peroxidase (LiP) and manganese peroxidase (MnP). The multistep pathway is initiated by a LiP- or MnP-catalyzed oxidative dechlorination reaction to produce 2,6-dichloro-1,4-benzoquinone. The quinone is reduced to 2,6-dichloro-1,4-dihydroxybenzene, which is reductively dechlorinated to yield 2-chloro-1,4-dihydroxybenzene. The latter is degraded further by one of two parallel pathways: it either undergoes further reductive dechlorination to yield 1,4-hydroquinone, which isortho-hydroxylated to produce 1,2,4-trihydroxybenzene, or is hydroxylated to yield 5-chloro-1,2,4-trihydroxybenzene, which is reductively dechlorinated to produce the common key metabolite 1,2,4-trihydroxybenzene. Presumably, the latter is ring cleaved with subsequent degradation to CO2. In this pathway, the chlorine at C-4 is oxidatively dechlorinated, whereas the other chlorines are removed by a reductive process in which chlorine is replaced by hydrogen. Apparently, all three chlorine atoms are removed prior to ring cleavage. To our knowledge, this is the first reported example of aromatic reductive dechlorination by a eukaryote.

scholarly journals Microbial degradation of alkylbenzenesulphonates. Metabolism of homologues of short alkyl-chain length by an Alcaligenes sp

1974 ◽  
Vol 140 (2) ◽  
pp. 121-134 ◽  
Author(s):  
J. Anthony Bird ◽  
Ronald B. Cain
Keyword(s):  
Alkyl Chain ◽  
Sole Source ◽  
Oxidation Products ◽  
Ring Cleavage ◽  
Growth Substrate ◽  
First Order ◽  
Heat Treated ◽  
Catechol 1,2 Dioxygenase ◽  
Benzene Toluene ◽  
Ortho Pathway

1. An organism isolated from sewage and identified as an Alcaligenes sp. utilized benzenesulphonate, toluene-p-sulphonate or phenylethane-p-sulphonate as sole source of carbon and energy for growth. Higher alkylbenzenesulphonate homologues and the hydrocarbons, benzene, toluene, phenylethane and 1-phenyldodecane were not utilized. 2. 2-Phenylpropanesulphonate was metabolized to 4-isopropylcatechol. 3. 1-Phenylpropanesulphonate was metabolized to an ortho-diol, which was tentatively identified, in the absence of an authentic specimen, as 4-n-propylcatechol. 4. In the presence of 4-isopropylcatechol, which inhibited catechol 2,3-dioxygenase, 4-ethylcatechol accumulated in cultures growing on phenylethane-p-sulphonate. 5. Authentic samples of catechol, 3-methylcatechol, 4-methylcatechol, 4-ethylcatechol and 3-isopropylcatechol were oxidized by heat-treated extracts to the corresponding 2-hydroxyalkylmuconic semialdehydes. Ring cleavage occurred between C-2 and C-3. 6. The catechol derived from 1-phenylpropanesulphonate was oxygenated by catechol 2,3-dioxygenase to a compound with all the properties of a 2-hydroxyalkylmuconic semialdehyde, but it was not rigorously identified. 7. The catechol 2,3-dioxygenase induced by growth on benzenesulphonate, toluene-p-sulphonate or phenylethane-p-sulphonate showed a constant ratio of specific activities with catechol, 3-methylcatechol, 4-methylcatechol and 4-ethylcatechol that was independent of the growth substrate. At 60°C, activity towards these substrates declined at an identical first-order rate. 8. Enzymes of the ‘ortho’ pathway of catechol metabolism were present in small amounts in cells grown on benzenesulphonate, toluene-p-sulphonate or phenylethane-p-sulphonate. 9. The catechol 1,2-dioxygenase oxidized the alkylcatechols, but the rates and the total extents of oxidation were less than for catechol itself. The oxidation products of these alkylcatechols were not further metabolized.

Oxidations with lead tetraacetate. IV. Oxidations of 1,3-benzodithioles

1983 ◽  
Vol 36 (12) ◽  
pp. 2499 ◽  
Author(s):  
C Aromdee ◽  
ER Cole ◽  
G Crank
Keyword(s):  
Carboxylic Acid ◽  
Lead Tetraacetate ◽  
Oxidation Products ◽  
Ring Cleavage ◽  
Methyl Group

Oxidations of 2,2-dialkyl and spiro[1,3-benzodithiole-2,1'-cycloalkanes] with lead tetraacetate gave mainly sulfoxides and disulfoxides. The stereochemistry of these products was elucidated by n.m.r. spectroscopy. Oxidation of 2-methyl-2-aryl derivatives gave sulfoxides as minor products; here the main products were derived from attack on the methyl group forming acetoxy, diacetoxy, formyl and carboxylic acid derivatives and ring cleavage products. 2,2-Diaryl derivatives also formed small amounts of sulfoxides but ring cleavage products were predominant. Monosubstituted benzodithioles were very reactive and produced a variety of oxidation products, mostly unidentified.

Photo-Fenton-like treatment of K-acid: assessment of treatability, toxicity and oxidation products

2014 ◽  
Vol 70 (6) ◽  
pp. 1056-1064 ◽  
Author(s):  
Tugba Olmez-Hanci ◽  
Idil Arslan-Alaton ◽  
Ozlem Gelegen
Keyword(s):  
Visible Light ◽  
Visible Light Irradiation ◽  
Vibrio Fischeri ◽  
Degradation Pathway ◽  
Oxidation Products ◽  
Light Irradiation ◽  
Ring Cleavage ◽  
Liquid Chromatograph ◽  
Commercially Important ◽  
Uv C

Photo-Fenton-like treatment of the commercially important naphthalene sulphonate K-acid (2-naphthylamine-3,6,8-trisulphonic acid) was investigated using UV-C, UV-A and visible light irradiation. Changes in toxicity patterns were followed by the Vibrio fischeri bioassay. Rapid and complete degradation of K-acid accompanied with nearly complete oxidation and mineralization rates (>90%) were achieved for all studied irradiation types. On the other hand, detoxification was rather limited and did not change significantly during photo-Fenton-like treatment. Several oxidation products could be identified via liquid chromatograph–mass spectrometer analyses, such as desulphonated and hydroxylated naphthalene derivatives, quinones, and ring-opening as well as dimerization products. Photo-Fenton-like treatment of K-acid with UV-C, UV-A and visible light irradiation occurred through a series of hydroxylation and desulphonation reactions, followed by ring cleavage. A common degradation pathway for photo-Fenton-like treatment of K-acid using different irradiation types was proposed.

Intradiol Aromatic Ring Cleavage in a Dioxygenase Model System

1981 ◽  
Vol 36 (10) ◽  
pp. 1324-1330 ◽  
Author(s):  
Dennis G. Brown ◽  
William J. Hughes
Keyword(s):  
Oxygen Consumption ◽  
Model System ◽  
Oxidation Products ◽  
Ring Cleavage ◽  
Secondary Oxidation ◽  
Isomeric Mixture ◽  
Aromatic Ring Cleavage ◽  
Phenanthroline Ligand ◽  
Kinetics Of

Abstract Dioxygenase Model, Copper, Catechol The complex (3-n-nonylcatecholato)(1,10-phenanthroline)copper(II) reacts with molecular oxygen to give an isomeric mixture of 2-n-nonylmuconic acid and several secondary oxidation products. The catecholato ligand is oxidatively cleaved in an intradiol fashion reminescent of the reactions catalyzed by intradiol aromatic dioxygenases. The 1,10-phenanthroline ligand can be quantitatively recovered and is not oxidized. In addition to characterization of oxidation products, the kinetics of oxygen consumption have been analyzed. The rate law for oxygen uptake is -d[O2]/dt = k[O2] [copper]2 .

The Anticoagulant Activity of 3.3’-(p-Alkylthio-Benzylidene)-Bis-4-Hydroxycoumarins and Their Oxidation Products

1967 ◽  
Vol 17 (01/02) ◽  
pp. 277-286 ◽  
Author(s):  
Maria Gumińska ◽  
M Eckstein ◽  
Barbara Stachurska ◽  
J Sulko
Keyword(s):  
Biological Activity ◽  
Anticoagulant Activity ◽  
Oxidation Products ◽  
Para Position ◽  
Sulphur Atom ◽  
Group I ◽  
One Step

SummaryThe anticoagulant activity of 3.3’-(benzylidene)-bis-4-hydroxycoumarin derivatives has been estimated by one step Quick’s method. The derivatives contained the following groups in the para position of benzylidene residue: NCS- (I), CH3-S- (II), CH3-SO-(III), CH3-S02- (IV), C2H5-S- (V), C2H5-SO- (VI), C2H5-S02- (VII). All these compounds were much more active than 3.3’-(benzylidene)-bis-4-hydroxycoumarin itself.Compounds possessing the ethyl chain at the sulphur atom (V, VI, VII) were more active than methyl homologues (II, III, IV). Comparison of the activity of the series of thio-, sulphoxy-, and sulphonyl-derivatives showed that among methyl- and ethyl-derivatives those with the sulphoxy grouping (III, VI) displayed the greatest anticoagulant activity. The action of sulphonyl (IV, VII) and thio-derivatives (II, V) was weaker and shortest. The derivative with the NCS-group (I) possessed a relatively the lowest activity among the investigated compounds. 3.3’-(p-Ethylsulphoxybenzyl-idene)-bis-4-hydroxycoumarin (VI), with distinct biological activity reached about ½ of dicoumarol activity.

Mechanistic Insights into Fe Catalyzed α-C-H Oxidations of Tertiary Amines

2019 ◽  
Author(s):  
Christopher J. Legacy ◽  
Frederick T. Greenaway ◽  
Marion Emmert
Keyword(s):  
Free Radical ◽  
Catalytic Mechanism ◽  
Catalyst System ◽  
Oxidation Products ◽  
Tertiary Amines ◽  
Catalyst Activation ◽  
Rate Determining Step ◽  
Fe Catalyst ◽  
Ligand Coordination ◽  
Rate Kinetics

We report detailed mechanistic investigations of an iron-based catalyst system, which allows the α-C-H oxidation of a wide variety of amines, including acyclic tertiary aliphatic amines, to afford dealkylated or amide products. In contrast to other catalysts that affect α-C-H oxidations of tertiary amines, the system under investigation employs exclusively peroxy esters as oxidants. More common oxidants (e.g. tBuOOH) previously reported to affect amine oxidations via free radical pathways do not provide amine α-C-H oxidation products in combination with the herein described catalyst system. Motivated by this difference in reactivity to more common free radical systems, the investigations described herein employ initial rate kinetics, kinetic profiling, Eyring studies, kinetic isotope effect studies, Hammett studies, ligand coordination studies, and EPR studies to shed light on the Fe catalyst system. The obtained data suggest that the catalytic mechanism proceeds through C-H abstraction at a coordinated substrate molecule. This rate-determining step occurs either at an Fe(IV) oxo pathway or a 2-electron pathway at a Fe(II) intermediate with bound oxidant. We further show via kinetic profiling and EPR studies that catalyst activation follows a radical pathway, which is initiated by hydrolysis of PhCO3 tBu to tBuOOH in the reaction mixture. Overall, the obtained mechanistic data support a non-classical, Fe catalyzed pathway that requires substrate binding, thus inducing selectivity for α-C-H functionalization.<br>

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