118-75-2Relevant articles and documents
Oxidation using [bis(trifluoroacetoxy)]iodobenzene: A new and potentially practical approach to detection of polychlorinated phenols
Saby, Coralie,Luong, John H. T.
, p. 1197 - 1198 (1997)
A novel oxidation for pentachlorophenol, 2,4,6-trichlorophenol and 2,3,5,6-tetrachlorophenol using [bis-(trifluoroacetoxy)]iodobenzene has been developed, and the oxidation products from pentachlorophenol and 2,3,5,6-tetrachlorophenol have been identified as tetrachloro-1,4-benzoquinone; this novel reaction can be applied in electrochemistry using glucose oxidase for sensitive determination and identification of PCP, one of the most toxic polychlorinated phenols.
Effect of oxalate and pH on photodegradation of pentachlorophenol in heterogeneous irradiated maghemite System
Lan, Qing,Cao, Meiyuan,Ye, Zhijun,Zhu, Jishu,Chen, Manjia,Chen, Xuequan,Liu, Chengshuai
, p. 198 - 206 (2016)
Photochemical degradation in the system of iron oxides and oxalic acid (OX) is the important reaction for detoxification of organic pollutants in natural environments, including surface soils, surface water, and even aerosols, and it was more effective at low pH according to previous studies. However, in this study, the photodegradation of pentachlorophenol (PCP) proceeded rapidly at different pH conditions in the system with maghemite and OX under UV light illumination. It was observed that the removal of PCP was 77.7% ± 0.90%, 79.9% ± 0.80% and 74.3% ± 1.50% at initial pH of 3.5, 5.0 and 7.0, respectively. To explore the degradation mechanism, the interaction of OX and maghemite were systematically studied as a function of pH. The presence of OX of 1.2 mM effectively decreased the iso-electric point (iep) of the maghemite from 5.6 to 1.8. The maximum adsorption amount of maghemite adsorbing OX increased with increasing pH value from 208 mmol kg-1 at pH = 3.5 to 293 mmol kg-1 at pH = 9.0. However, PCP (0.0375 mM) inhibited the adsorption of oxalic acid at pH = 3.5 and pH = 5.0 but promoted it at pH = 7.0 and pH = 9.0. When the initial content of OX was 1.2 mM, the highly active compounds of Fe(C2O4)33- as Fe(III) and Fe(C2O4)22- as Fe(II) were the dominant species at different pH. The formation of H2O2 also relied on the value of pH and the concentration range of H2O2 during PCP degradation was 0-1.67 mg L-1, 0-1.16 mg L-1 and 0-0.16 mg L-1at initial pH of 3.5, 5.0 and 7.0, respectively. The low pH conditions favored the iron cycling, the H2O2 generation and the broken of aromatic ring of PCP, so as to enhance the degradation rates of PCP. At the high pH conditions, due to the slowdown of the iron cycling and the decreased amount of H2O2 formation, the direct photolysis was responsible for the enhanced degradation of PCP. The foundation of high photochemical efficiencies of OX and maghemite for PCP degradation at large-scale pH conditions improves the photochemical mechanisms of OX-iron oxide system and is of important for understanding the transformation of organic pollutants in light environments.
Azido bridge mediated catecholase activity, electrochemistry and magnetic behavior of a dinuclear copper(II) complex of a phenol based "end-off" compartmental ligand
Chakraborty, Prateeti,Majumder, Ishani,Kara, Hulya,Chattopadhyay, Shyamal Kumar,Zangrando, Ennio,Das, Debasis
, p. 139 - 145 (2015)
Abstract A dinuclear Cu(II) species [Cu2L2(H2O)2(N3)](NO3)2 (L = 2,6-bis(N-ethylpyrrolidine-iminomethyl)-4-methyl-phenolato) where two Cu centers are bridged by phenoxido and μ1,1-azido bridges with Cu-Cu separation of ～3 ? have been synthesized with the view to explore the role of azido bridge on catecholase activity and electrochemical property and the roles of both the bridging groups on magnetic coupling of two copper centers. The complex exhibits excellent catecholase activity in acetonitrile as well as in DMSO medium not only by oxidizing 3,5-di-tert-butylcatechol (3,5-DTBC) but also tetrachlorocatechol (TCC), a catechol which is very thorny to oxidize, under aerobic conditions and becomes the first example of its own kind. CV study reveals three quasi-reversible reductive couples which are tentatively assigned as Cu2II to CuIICuI and CuICuI reduction followed by reduction of CuICuI complex to Cu0Cu0 species. Variable temperature magnetic study suggests the presence of an antiferromagnetic spin-exchange interaction between Cu(II) ions in the dimer via double bridge where the antiferromagnetic contribution of phenoxido bridge predominates over the ferromagnetic interaction of azido bridge.
Activation of electron transfer reduction of p-benzoquinone derivatives by intermolecular regioselective hydrogen bond formation
Fukuzumi, Shunichi,Kitaguchi, Hironori,Suenobu, Tomoyoshi,Ogo, Seiji
, p. 1984 - 1985 (2002)
Electron transfer reduction of p-benzoquinones by cobalt tetraphenylporphyrin is enhanced significantly by the presence of o-bis(phenylcarbamoylmethyl)benzene (o-L) due to the regioselective hydrogen bond formation between the corresponding semiquinone ra
Coexistence of Hydrogen Atom Transfer Reactions through and not through Triplet Ion Pair between p-Chloranil and Durene
Kobashi, Harumichi,Funabashi, Masa-aki,Kondo, Tomoyuki,Morita, Toshifumi,Okada, Tadashi,Mataga, Noboru
, p. 3557 - 3565 (1984)
Mechanism of hydrogen atom abstraction reactions by triplet state p-chloranil (3CA) from durene (DH) were studied by picosecond and nanosecond laser photolysis and transient photoconductivity measurements. 3CA was quenched by DH through diffusional encounter to form a triplet ion pair (IP) between CA and DH, p-chloranil semiquinone radical (CAH.), and 2,4,5-trimethylbenzyl radical (D.).Ionic dissociation of IP was observed in 1,2-dichloroethane (DCE) as well as in acetonitrile.However, no transient species was observed by direct excitation of a charge-transfer (CT) band of the electron donor-acceptor (EDA) complex between CA and DH.The H-atom transfer leading to production of CAH. was found to proceed through two distinct mechanisms; H-atom transfer via IP (Mechanism I) and a more rapid transfer competing with IP formation (Mechanism II).The quantum yields of CAH. produced by Mechanism I and II and the first-order rate constants for proton transfer, ionic dissociation, and intersystem crossing competing with one another in the IP state were estimated to be (0.1 and 0.2) and (2,5, and 13)X106 s-1, respectively, in DCE at room temperature.
A flow injection (FI) biosensor system for pentachlorophenol (PCP) using a substance recycling scheme
Labra-Espina, Marietta,Male, Keith B.,Luong, John H. T.
, p. 3291 - 3295 (2000)
A flow injection (FI) biosensor system has been designed for the analysis of pentachlorophenol (PCP) using a substrate recycling scheme comprising immobilized bilirubin oxidase (BOX) in the presence of excess of NADH. PCP was efficiently converted to tetrachloro-p-benzoquinone (1,4-TCBQ) and then tetrachloro-p-hydroquinone (1,4-TCHQ) by bis(trifluoroacetoxy)iodobenzene (BTFAIB) and zinc powder, respectively. BOX immobilized on aminopropyl glass beads rapidly oxidized 1,4-TCHQ to 1,4-TCBQ, which in turn was readily reduced back to 1,4-TCHQ in the presence of excess NADH. This recycling scheme enabled one molecule of PCP to consume several NADH molecules leading to enhanced sensitivity. Under optimized conditions the rate of NADH uptake measured as the absorbance decrease at 340 nm yielded a detection limit for 1,4-TCHQ or oxidized PCP of 250 nM. The detection limit was improved to 25 nM for both analytes using a fluorescence detector with excitation and emission wavelengths of 345 and 450 nm, respectively. The PCP level in contaminated soil samples was measured using the FI biosensor system, and the results obtained compared well with capillary zone electrophoresis (CZE) analysis. A flow injection (FI) biosensor system has been designed for the analysis of pentachlorophenol (PCP) using a substrate recycling scheme comprising immobilized bilirubin oxidase (BOX) in the presence of excess of NADH. PCP was efficiently converted to tetrachloro-p-benzoquinone (1,4-TCBQ) and then tetrachloro-p-hydroquinone (1,4-TCHQ) by bis(trifluoroacetoxy)iodobenzene (BTFAIB) and zinc powder, respectively. BOX immobilized on aminopropyl glass beads rapidly oxidized 1,4-TCHQ to 1,4-TCBQ, which in turn was readily reduced back to 1,4-TCHQ in the presence of excess NADH. This recycling scheme enabled one molecule of PCP to consume several NADH molecules leading to enhanced sensitivity. Under optimized conditions the rate of NADH uptake measured as the absorbance decrease at 340 nm yielded a detection limit for 1,4-TCHQ or oxidized PCP of 250 nM. The detection limit was improved to 25 nM for both analytes using a fluorescence detector with excitation and emission wavelengths of 345 and 450 nm, respectively. The PCP level in contaminated soil samples was measured using the FI biosensor system, and the results obtained compared well with capillary zone electrophoresis (CZE) analysis.
Peroxidase-Catalyzed Oxidation of Pentachlorophenol
Samokyszyn, Victor M.,Freeman, James P.,Maddipati, Krishna Rao,Lloyd, Roger V.
, p. 349 - 355 (1995)
Pentachlorophenol (PCP) was shown to function as a reducing substrate for horseradish peroxidase (HRP) and to stimulate the HRP-catalyzed reduction of 5-phenyl-4-penten-1-yl hydroperoxide (PPHP) to 5-phenyl-4-penten-1-ol. HRP catalyzed the hydroperoxide-dependent oxidation of PCP, using H2O2, PPHP, or ethyl hydroperoxide as substrates, as evidenced by UV spectroscopic and reverse phase HPLC analysis of reaction mixtures. The major oxidation product was tetrachloro-1,4-benzoquinone which was identified on the basis of electronic absorption spectroscopy, mass spectrometry, and cochromatography with authentic standard. HRP-catalyzed oxidation of PCP yielded relatively stable, ESR-detectable pentachlorophenoxyl radical intermediates whose ESR spectra consisted of a symmetrical single line without hyperfine structure. Substitution of natural abundance isotopically-labeled PCP with 13C-labeled PCP resulted in broadening of the ESR signal line width from 6.1 G to 13.5 G. ESR spin trapping studies, with α-(1-oxy-4-pyridyl)-N tert-butylnitrone (4-POBN) as the spin trap demonstrated identical spectra using natural abundance isotopically-labeled PCP versus 13C-labeled PCP, suggesting oxyl addition, rather than carbon-centered radical addition to 4-POBN. The computer simulation of the observed spectra is consistent with two distinct 4-POBN adducts, with relative abundances of ca. 3:1, and hyperfine coupling constants of aN = (14.61 G)/aH = 1.83 G and aN = (14.76 G)/aH = 5.21 G, respectively. Mechanisms for the hydroperoxide-dependent, HRP-catalyzed oxidation of PCP are presented that are consistent with these results.
Photocatalytic Hydrogen Evolution from Plastoquinol Analogues as a Potential Functional Model of Photosystem I
Fukuzumi, Shunichi,Hong, Young Hyun,Lee, Yong-Min,Nam, Wonwoo
, p. 14838 - 14846 (2020)
The recent development of a functional model of photosystem II (PSII) has paved a new way to connect the PSII model with a functional model of photosystem I (PSI). However, PSI functional models have yet to be reported. We report herein the first potential functional model of PSI, in which plastoquinol (PQH2) analogues were oxidized to plastoquinone (PQ) analogues, accompanied by hydrogen (H2) evolution. Photoirradiation of a deaerated acetonitrile (MeCN) solution containing hydroquinone derivatives (X-QH2) as a hydrogen source, 9-mesityl-10-methylacridinium ion (Acr+-Mes) as a photoredox catalyst, and a cobalt(III) complex, CoIII(dmgH)2pyCl (dmgH = dimethylglyoximate monoanion; py = pyridine) as a redox catalyst resulted in the evolution of H2 and formation of the corresponding p-benzoquinone derivatives (X-Q) quantitatively. The maximum quantum yield for photocatalytic H2 evolution from tetrachlorohydroquinone (Cl4QH2) with Acr+-Mes and CoIII(dmgH)2pyCl and H2O in deaerated MeCN was determined to be 10%. Photocatalytic H2 evolution is started by electron transfer (ET) from Cl4QH2 to the triplet ET state of Acr+-Mes to produce Cl4QH2?+ and Acr?-Mes with a rate constant of 7.2 × 107 M-1 s-1, followed by ET from Acr?-Mes to CoIII(dmgH)2pyCl to produce [CoII(dmgH)2pyCl]-, accompanied by the regeneration of Acr+-Mes. On the other hand, Cl4QH2?+ is deprotonated to produce Cl4QH?, which transfers either a hydrogen-atom transfer or a proton-coupled electron transfer to [CoII(dmgH)2pyCl]- to produce a cobalt(III) hydride complex, [CoIII(H)(dmgH)2pyCl]-, which reacts with H+ to evolve H2, accompanied by the regeneration of CoIII(dmgH)2pyCl. The formation of [CoII(dmgH)2pyCl]- was detected by electron paramagnetic resonance measurements.
Substrate recycling scheme for tetrachloro-p-benzoquinone using bilirubin oxidase and NADH: Application for pentachlorophenol assay
Cybulski, David,Male, Keith B.,Scharer, Jeno M.,Moo-Young, Murray,Luong, John H. T.
, p. 796 - 800 (1999)
A novel assay for tetrachloro-p-benzoquinone (TCBQ), the main oxidation product of pentachlorophenol (PCP), was developed using bilirubin oxidase (BOX) in the presence of excess NADH. TCBQ was easily and rapidly reduced by NADH to 1,4-tetrachlorohydroquinone (TCHQ), which was then recycled back to TCBQ by the enzyme. BOX exhibited no reactivity toward NADH while its catalytic activity for the oxidation of TCHQ was very high. Under an optimized condition (250 μM NADH, 0.3 U/mL BOX, and 25 mM sodium phosphate at pH 5.5), the rate of NADH consumption determined by measuring the absorbance decrease at 340 nm yielded a detection limit for TCBQ of 110 nM. Fluorescence detection of the NADH using a lower enzyme concentration (0.1 U/mL) with excitation and emission wavelengths of 345 and 450 nm, respectively, allowed for a TCBQ detection limit of 30 nM. PCP was oxidized to TCBQ with high yield using bis(trifluoroacetoxy)iodobenzene in 0.05 M trichloroacetic acid. Coupling this oxidation reaction to the BOX/NADH assay attained PCP detection limits of 170 and 50 nM using absorbance and fluorescence measurements, respectively. When tested on PCP-contaminated soil samples, the BOX assay compared very well with HPLC measurements. Chlorophenols constitute a major group of pollutants having been widely used as wood preservatives, pesticides, and herbicides. They are also formed as byproducts of many industrial activities including chlorination of potable water and paper bleaching. A novel assay for tetrachloro-p-benzoquinone (TCBQ), the main oxidation product of pentachlorophenol (PCP), was developed using bilirubin oxidase (BOX) in the presence of excess NADH. TCBQ was easily and rapidly reduced by NADH to 1,4-tetrachlorohydroquinone (TCHQ), which was then recycled back to TCBQ by the enzyme. BOX exhibited no reactivity toward NADH while its catalytic activity for the oxidation of TCHQ was very high. Under an optimized condition (250 μM NADH, 0.3 U/mL BOX, and 25 mM sodium phosphate at pH 5.5), the rate of NADH consumption determined by measuring the absorbance decrease at 340 nm yielded a detection limit for TCBQ of 110 nM. Fluorescence detection of the NADH using a lower enzyme concentration (0.1 U/mL) with excitation and emission wavelengths of 345 and 450 nm, respectively, allowed for a TCBQ detection limit of 30 nM. PCP was oxidized to TCBQ with high yield using bis(trifluoroacetoxy)iodobenzene in 0.05 M trichloroacetic acid. Coupling this oxidation reaction to the BOX/NADH assay attained PCP detection limits of 170 and 50 nM using absorbance and fluorescence measurements, respectively. When tested on PCP-contaminated soil samples, the BOX assay compared very well with HPLC measurements.
Primary product of the horseradish peroxidase-catalyzed oxidation of pentachlorophenol
Kazunga, Chikoma,Aitken, Michael D.,Gold, Avram
, p. 1408 - 1412 (1999)
Peroxidases are a class of enzymes that catalyze the oxidation of various phenolic substrates by hydrogen peroxide. They are common enzymes in soil and are also available commercially, so that they have been proposed as agents of phenolic pollutant transformation both in the environment and in engineered systems. Previous research on the peroxidase-catalyzed oxidation of pentachlorophenol (PCP) has suggested that tetrachloro-p-benzoquinone (chloranil) is the principal product and that a considerable fraction of the PCP added to reaction mixtures appears to be resistant to oxidation. In experiments employing alternative methods of product separation and analysis, we found that both of these observation s are artifacts of extraction and analytical methods used in previous studies. The major product of the horseradish peroxidase-catalyzed oxidation of pentachlorophenol from pH 4-7 was 2,3,4,5,6-pentachloro-4-pentachlorophenoxy-2,5-cyclohexadienone (PPCHD), which is formed by the coupling of two pentachlorophenoxyl radicals. The yield of chloranil and other soluble products was negligible. PPCHD is insoluble and unreactive in aqueous media but is reactive when dissolved in various organic solvents. Substantia amounts of chloranil were formed when PPCHD was dissolved in benzene, ethyl acetate, or methanol; less was formed in hexane and acetonitrile; and negligible amounts were formed in dimethylformamide. High-pressure liquid chromatography (HPLC) analysis of PPCHD indicated that it is capable of undergoing dissociation and reduction to pentachloro phenol under typical reversed-phase HPLC conditions. Chlorinated oligomeric products are formed when PPCHD is stored in acetonitrile, either alone or with added pentachlorophenol. Our results demonstrate that the removal of PCP in peroxidase-catalyzed reactions can be much higher than indicated in previous work, as long as the initial product is separated by filtration or other physical means. The major product of the horseradish peroxidase-catalyzed oxidation of pentachlorophenol from pH 4-7 was 2,3,4,5,6-pentachloro-4-pentachlorophenoxy-2,5-cyclohexadienone (PPCHD), which is formed by the coupling of two pentachlorophenoxyl radicals. PPCHD is insoluble and unreactive in aqueous media but is reactive when dissolved in various organic solvents. High pressure liquid chromatography (HPLC) analysis of PPCHD indicated that it is capable of undergoing dissociation and reduction to pentachlorophenol under typical reversed-phase HPLC conditions. The removal of pentachlorophenol in peroxidase-catalyzed reactions can be much higher as long as the initial product is separated by filtration or other physical means.
