- Metal-free, air-promoted, radical-mediated arylation of benzoquinone with phenylhydrazines
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An efficient, economic, and air-promoted metal-free method for direct arylation of benzoquinone with phenylhydrazines was developed. This approach leads to the formation of corresponding [1,1′-biphenyl]-2,5-dione derivatives as biological and pharmaceutic
- Sayahi, Mohammad Hosein,Ansari, Samira,Saghanezhad, Seyyed Jafar,Mahdavi, Mohammad
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- Direct UV-written highly fluorinated aromatic-aliphatic copolyethers for optical waveguides
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A bisphenol monomer (4-methoxy) phenylhydroquinone (Me-HQ) was prepared and further polymerized with 2,2,3,3,4,4,5,5,6,6,7,7-dodeca-fluoro-1,8-octanediol (12F-diol) and decafluorobiphenyl (DFBP) to obtain highly fluorinated aromatic-aliphatic copolyethers containing methoxy groups. After demethylation and the reaction with epoxy chloropropane, a series of novel highly fluorinated aromaticaliphatic copolyethers bearing epoxy groups (FA-APE EP) at different feed ratios of (Me-HQ)/(12F-diol) were obtained. The chemical structures of all the copolymers were analyzed by 1H NMR, 13C NMR and 19F NMR spectra. A series of highly fluorinated photoresists were prepared by composing of fluorinated copolyethers, diphenyliodonium salt as a photoacid generator (PAG) and solvent. After UV-curing, the cross-linked films exhibited excellent chemical resistance and high thermal stability (Td ranged from 230 to 278 -C). The refractive indices of the films could be controlled between 1.5127 and 1.4749 at 1550 nm by varying the feed ratio of comonomers. A clear negative pattern was obtained through direct UV exposure and chemical development. For waveguides without upper cladding, the propagation loss of the channel waveguides was measured to be 0.18 dB/cm at 1550 nm.
- Wan, Ying,Zhang, Yang,Shi, Zuosen,Xu, Wenhui,Zhang, Xiaolong,Zhao, Lisha,Cui, Hanchen
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- Chemoproteomics of an indole-based quinone epoxide identifies druggable vulnerabilities in vancomycin-resistant staphylococcus aureus
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The alarming global rise in fatalities from multidrug-resistant Staphylococcus aureus (S. aureus) infections has underscored a need to develop new therapies to address this epidemic. Chemoproteomics is valuable in identifying targets for new drugs in different human diseases including bacterial infections. Targeting functional cysteines is particularly attractive, as they serve critical catalytic functions that enable bacterial survival. Here, we report an indole-based quinone epoxide scaffold with a unique boat-like conformation that allows steric control in modulating thiol reactivity. We extensively characterize a lead compound (4a), which potently inhibits clinically derived vancomycin-resistant S. aureus. Leveraging diverse chemoproteomic platforms, we identify and biochemically validate important transcriptional factors as potent targets of 4a. Interestingly, each identified transcriptional factor has a conserved catalytic cysteine residue that confers antibiotic tolerance to these bacteria. Thus, the chemical tools and biological targets that we describe here prospect new therapeutic paradigms in combatting S. aureus infections.
- Kulkarni, Amogh,Soni, Isha,Kelkar, Dhanashree S.,Dharmaraja, Allimuthu T.,Sankar, Rathinam K.,Beniwal, Gaurav,Rajendran, Abinaya,Tamhankar, Sharvari,Chopra, Sidharth,Kamat, Siddhesh S.,Chakrapani, Harinath
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supporting information
p. 6785 - 6795
(2019/08/20)
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- C-H arylation reactions through aniline activation catalysed by a PANI-g-C3N4-TiO2 composite under visible light in aqueous medium
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A PANI (polyaniline)-g-C3N4-TiO2 composite was prepared and found to be efficient for radical C-H arylation reactions. The arylation process involved coupling of in situ generated aryl diazonium salts from aniline with heteroarenes, enol acetates or benzoquinones under visible light in aqueous medium or pure water. A broad range of substrates survived the reaction conditions to provide the desired products in moderate to good yields. Scale-up (10 mmol) synthesis was also achieved. This semiconductor photocatalyst showed good photocatalytic performance and stability. Recycle studies showed that this composite could be readily recovered and a slight decrease in the catalytic activity was observed after ten consecutive runs.
- Wang, Liang,Shen, Jun,Yang, Sen,Liu, Wenjie,Chen, Qun,He, Mingyang
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supporting information
p. 1290 - 1296
(2018/03/26)
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- Hydroquinone-Based Biarylic Polyphenols as Redox Organocatalysts for Dioxygen Reduction: Dramatic Effect of Orcinol Substituent on the Catalytic Activity
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A series of 18 new biaryls has been synthesized and investigated with regard to their organocatalytic efficiency. They consist of a hydroquinone core linked to a phenol or a resorcinol moiety. It is shown that the resorcinol moiety substituted on its meta position has a strong impact on the catalytic activities of these compounds towards the reduction of dioxygen by diethylhydroxylamine (DEHA) in aqueous medium. While the derivative consisting of the two cores spaced by three methylene units is completely inactive, substitution on the hydroquinone part leads to tremendously active catalysts, especially the biaryl consisting of methoxyhydroquinone-orcinol. Two mechanisms are proposed to explain the dramatic efficiency of the novel hydroquinone-based biarylic polyphenols for the catalytic reduction of dioxygen, both considering the influence of the orcinol moiety on the semiquinone anion intermediate. As a first hypothesis, this substituent could promote its direct reduction by DEHA to regenerate the hydroquinone, which will react again to regenerate the semiquinone. On the other hand, an intramolecular hydrogen bond could enhance the reactivity of the semiquinone anion toward dioxygen by an addition–elimination mechanism. In this case, the elimination would provide the corresponding quinone but, since the reduction of the quinones by DEHA is much slower than the observed kinetics, a reduction by DEHA prior to the elimination has to be considered to generate the semiquinone anion instead of the quinone. (Figure presented.).
- Lebeuf, Rapha?l,Nardello-Rataj, Véronique,Aubry, Jean-Marie
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p. 268 - 278
(2017/02/05)
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- Ir-catalyzed arylation, alkylation of quinones with boronic acids through C-C coupling
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Ir-catalyzed arylation, alkylation of quinones with boronic acids was developed under room temperature. Both aryl and alkyl boronic acids are suitable for this transformation. This expands the application scope of the iridium catalyst. This is also an excellent proof that iridium catalysts can be used in the C-C coupling of quinones and naphthoquinones with alkyl boronic acids.
- Wang, Dawei,Ge, Bingyang,Ju, Anqi,Zhou, Yucheng,Xu, Chongying,Ding, Yuqiang
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supporting information
p. 30 - 33
(2015/01/30)
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- Synthesis of aryl substituted quinones as β-secretase inhibitors: Ligand-free direct arylation of quinones with aryl halides
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The simple ligand-free direct arylation of quinones with aryl halides applying Pd(OAc)2as a catalyst in accordance with Heck reaction was studied. This reaction provided a simple and efficient synthetic approach to efficient inhibitors of β-secretase aryl-substituted quinones.
- Wang, Dawei,Ge, Bingyang,Yang, Shuyan,Miao, Hongyan,Ding, Yuqiang
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p. 1615 - 1621
(2015/02/19)
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- Transition metal-free direct C-H functionalization of quinones and naphthoquinones with diaryliodonium salts: Synthesis of aryl naphthoquinones as β-secretase inhibitors
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A novel ligand-free, transition metal-free direct C.H functionalization of quinones with diaryliodonium salts has been developed for the first time. The transformation was promoted only through the use of a base and gave aryl quinone derivatives in moderate to good yields. This methodology provided an effective and easy way to synthesize β-secretase inhibitors. The radical trapping experiments showed that this progress was the radical mechanism.
- Wang, Dawei,Ge, Bingyang,Li, Liang,Shan, Jie,Ding, Yuqiang
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p. 8607 - 8613
(2015/01/08)
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- Generation of arylated quinones by iron-catalyzed oxidative arylation of phenols: Formal synthesis of phellodonin, sarcodonin ε, leucomelone and betulinan A
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Biologically and pharmaceutically relevant arylated quinones (Quin-Ar) have been synthesized via direct C-H arylation of a variety of phenols using arylboronic acids. An inexpensive, environmentally friendly iron catalyst, ferric sulphate, Fe2(SO4)3, was employed in this operationally simple and efficient method.
- Deb, Arghya,Agasti, Soumitra,Saboo, Tapish,Maiti, Debabrata
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supporting information
p. 705 - 710
(2014/04/03)
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- Palladium-catalyzed direct C-H functionalization of benzoquinone
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A direct Pd-catalyzed C-H functionalization of benzoquinone (BQ) can be controlled to give either mono- or disubstituted BQ, including the installation of two different groups in a one-pot procedure. BQ can now be directly functionalized with aryl, heteroaryl, cycloalkyl, and cyclo-alkene groups and, moreover, the reaction is conducted in environmentally benign water or acetone as solvents.
- Walker, Sarah E.,Jordan-Hore, James A.,Johnson, David G.,MacGregor, Stuart A.,Lee, Ai-Lan
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supporting information
p. 13876 - 13879
(2015/02/05)
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- Synthesis of aryl- and alkylquinones through rhodium-catalyzed C-C coupling under mild conditions
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A direct arylation, alkylation of quinones with aryl and alkyl boronic acids through rhodium-catalyzed C-C coupling has been developed under mild conditions. [CpRhCl2]2 was shown to be the most effective catalyst for the transformation. More importantly, good to excellent yields were obtained under room temperature and base-free conditions. This reaction provides a practical, efficient method for the synthesis of aryl- and alkylquinones.
- Wang, Dawei,Ge, Bingyang,Du, Liyong,Miao, Hongyan,Ding, Yuqiang
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supporting information
p. 2895 - 2898
(2015/02/02)
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- Substituent effects on reactive oxygen species (ROS) generation by hydroquinones
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In order to understand the structural aspects of stabilization of hydroquinones and their ability to generate reactive oxygen species (ROS), we designed and synthesized a series of 6-aryl-2,3-dihydro-1,4-benzoquinones. These compounds equilibrate with the corresponding 6-aryl-1,4-dihydroxybenzenes in an organic medium; a linear free energy relationship analysis gave ρ = +2.37, suggesting that this equilibrium was sensitive to electronic effects. The propensity of the compound to enolize appears to determine ROS-generating capability, thus offering scope for tunable ROS generation.
- Dharmaraja, Allimuthu T.,Jain, Charu,Chakrapani, Harinath
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supporting information
p. 9413 - 9417
(2014/12/12)
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- C-H arylation of benzoquinone in water through aniline activation: Synergistic effect of graphite-supported copper oxide nanoparticles
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A homemade CuONPs/Gr catalyst was found to be efficient for the C-H arylation of benzoquinone. This methodology represents the first example of a Meerwein arylation catalyzed by a heterogeneous catalyst.
- Honraedt, Aurelien,Le Callonnec, Francois,Le Grognec, Erwan,Fernandez, Vincent,Felpin, Francois-Xavier
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p. 4604 - 4609
(2013/06/05)
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- Iron-catalyzed cross-coupling of electron-deficient heterocycles and quinone with organoboron species via innate C-H functionalization: Application in total synthesis of pyrazine alkaloid botryllazine A
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Here, we report an iron-catalyzed cross-coupling reaction of electron-deficient heterocycles and quinone with organoboron species via innate C-H functionalization. Iron(II) acetylacetonate along with oxidant (K 2S2O8) and phase-transfer catalyst (TBAB) under open flask conditions efficiently catalyzed the cross-coupling of pyrazine with arylboronic acids and gave monoarylated products in good to excellent yields. Optimized conditions also worked for other heterocylces such as quinoxalines, pyridines, quinoline, and isoquinoline as well as quinones. In addition, we demonstrated as a first example its application for the synthesis of anticancer marine pyrazine alkaloid botryllazine A.
- Singh, Parvinder Pal,Aithagani, Sravan Kumar,Yadav, Mahipal,Singh, Varun Pratap,Vishwakarma, Ram A.
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p. 2639 - 2648
(2013/04/24)
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- The direct arylation of benzoquinones with arylboronic acid promoted by iron(II) oxalate
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Arylations of various quinones with several arylboronic acids have been developed. The reactions proceed readily at ambient temperature using iron(II) oxalate as a catalyst and potassium persulfate as a co-oxidant. The mechanism is presumed to proceed through a nucleophilic radical addition to the quinone with in situ reoxidation of the resulting dihydroquinone.
- Huanga, Yibo,Guanb, Dan
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p. 649 - 651
(2014/01/17)
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- FeSO4-promoted direct arylation of benzoquinones with ArB(OH)2 or ArBF3K
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FeSO4·7H2O was proven to work as effective promoter for the direct arylation of benzoquinones with aryl boronic acids in the presence of K2S2O8. In the arylation, slow addition of iron solution was crucial to efficiently proceed with the reaction. Interestingly, the Fe-mediated arylation could be converted into a catalytic reaction by using hydroquinones, instead of benzoquinones, or addition of ascorbic acid.
- Komeyama, Kimihiro,Kashihara, Tetsuya,Takaki, Ken
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supporting information
p. 1084 - 1086
(2013/04/10)
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- Iron-mediated direct arylation with arylboronic acids through an aryl radical transfer pathway
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A novel iron-mediated direct C-H arylation of quinones and pyridine analogues with arylboronic acids has been developed using dichloromethane and water as solvents at ambient temperature. FeS is employed and serves as an efficient catalyst. A detailed reaction mechanism is speculated and expounded.
- Wang, Jian,Wang, Shan,Wang, Gao,Zhang, Ji,Yu, Xiao-Qi
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supporting information
p. 11769 - 11771
(2013/01/15)
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- Practical C-H functionalization of quinones with boronic acids
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A direct functionalization of a variety of quinones with several boronic acids has been developed. This scalable reaction proceeds readily at room temperature in an open flask using inexpensive reagents: catalytic silver(I) nitrate in the presence of a persulfate co-oxidant. The scope with respect to quinones is broad, with a variety of alkyl- and arylboronic acids undergoing efficient cross-coupling. The mechanism is presumed to proceed through a nucleophilic radical addition to the quinone with in situ reoxidation of the resulting dihydroquinone. This method has been applied to complex substrates, including a steroid derivative and a farnesyl natural product.
- Fujiwara, Yuta,Domingo, Victoriano,Seiple, Ian B.,Gianatassio, Ryan,Del Bel, Matthew,Baran, Phil S.
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supporting information; experimental part
p. 3292 - 3295
(2011/05/03)
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- Studies on the Meerwein Arylation-Based Preparation of 2,3-Diarylbenzene-1,4-diones and Its Theoretical Interpretation
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Title compounds possessing a variety of substituents are systematically prepared by means of Meerwein arylation of benzene-1,4-dione. Synthetic aspects and their MNDO calculation-based interpretation are described.
- Takahashi, Ichiro,Muramatsu, Osamu,Fukuhara, Jun,Hosokawa, Yoshinao,Takeyama, Naohiko,et al.
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p. 465 - 468
(2007/10/02)
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- Liquid-Crystalline Main-Chain Polyesters with Lateral Aromatic Substituents
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Varying the structure of common main-chain polymers, a series of new mostly liquid-crystalline polyesters with y-shaped mesogens derived from hydroquinone diacetate with different lateral aromatic substituents (4-methoxyphenyl, 4-biphenyl) and 4,4'-alkylenedioxybenzoic acids was synthesized.At given lateral group, the number of methylene units separating the aromatic ester triade mesogens ranges up to ten.First structure-property relationships could be determined using optical microscopy, differential scanning calorimetry and X-ray diffraction techniques.Corresponding to other types of liquid-crystalline polymers with laterally stressed mesogenic units, the anisotropic melts of our polyesters are nematic phases.Furthermore, X-ray investigations give hints to the existence of cybotactic groups.With increasing lateral substituents the lowering of the isotropization temperatures is accompanied by an enhanced tendency to form anisotropic glasses.Therefore, also polymers consisting of highly branched mesogenic building stones can form mesophases within a wide temperature interval.
- Roetz, U.,Lindau, J.,Fischer, H.,Kuschel, F.
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p. 167 - 174
(2007/10/02)
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- Reactive dyestuffs
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Triphendioxazine reactive dyestuffs of the general formula STR1 with the substituent definition given in the description, are outstandingly suitable for dyeing and printing materials containing hydroxyl groups or amide groups. They give red dyeings with high wet- and light-fastnesses.
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- Reduction of Arenediazonium Salts by Hydroquinone. Kinetics and Mechanism for the Electron-Transfer Step
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Arenediazonium tetrafluoroborate salts undergo facile electron transfer reaction with hydroquinone in aqueous phosphate-buffered solutions containing the hydrogen donor solvent acetonitrile.Reaction rates are the first-order in hydroquinone and arenediazonium ion concentrations, and they exhibit inverse first order dependence on the hydrogen ion concentration over the pH range of 1.0-9.5.Benzoquinone and arene are the principial products, but arylation of acetonitrile and benzoquinone are competitive in a reaction process that exhibits a 2:1 stoichiometric relationship between the arenediazonium ion salt and hydroquinone.Rate constants for reduction of substituted benzediazonium ions by the monoanion of hydroquinone correlate with ? constants yielding a ρ value of 3.5.Reactions performed in deuterium oxide show kinetic isotope effects that reflect the solvent isotope effect on the acidity constant for hydroquinone, and levels of isotope incorporation by deuterium abstraction from deuterium oxide and/or acetonitrile-d3 demonstrate that neither water nor hydroquinone are hydrogen atom donors to intermediate aryl radicals.Reduction of arenediazonium ions involves a rate-limiting single electron transfer from the monoanion of hydroquinone followed by a rapid single electron transfer from the semiquinone intermediate to the diazonium ion.Application of Marcus theory provides calculated rate constants for electron transfer from the hydroquinone monoanion to arenediazonium ions.These rate constants, together with the absence of evidence for a diazo ether intermediate and rate constants for diazotate formation, suggest that electron transfer occurs by an outer-sphere mechanism.
- Brown, Kathlynn C.,Doyle, Michael P.
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p. 3255 - 3261
(2007/10/02)
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- Triphendioxazine dyestuffs
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Triphendioxazine dyestuffs of the formula STR1 having the substituent meanings specified in the descriptive part, are highly suitable for dyeing and printing hydroxyl- or amido-containing materials, in particular fibre materials, and produce wash-fast dyeings and prints.
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- Mechanism of the Oxidation of NADH by Quinones. Energetics of One-Electron and Hydride Routes
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The kinetics of NADH oxidation by 7 o-benzoquinones and 14 p-benzoquinones were studied by using buffered aqueous solutions and UV/vis spectroscopy.For each quinone the rate law was first order in NADH and first order in quinone.The rate constants varied from 0.0745 to 9220 M-1s-1.Variation of the pH from 6 to 8 gave no change in rate.The use of 4-D and 4,4-D2NADH revealed kinetic isotope effects.The dideutero data gave kH/kD in the range 1.6-3.1 for p-quinones and 4.2 for 3,5-di-tert-butyl-o-quinone.When p-quinones were used, the log k was a linear function of Eo for the quinone/hydroquinone monoanion (Q/QH(1-)) couple with a slope of 16.9 V-1. o-Quinones reacted about 100 times more rapidly, but the same linear relationship with a slope of 16.4 V-1 was observed.Comparisons to data for one-electron-transfer reactions indicate that such mechanisms are not involved.A hydride-transfer mechanism accommodates all the data, and rate-limiting hydrogen atom transfer followed by electron transfer cannot be ruled out.
- Carlson, Brian W.,Miller, Larry L.
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p. 479 - 485
(2007/10/02)
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- Stabilized polyglycol for high temperatures
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A composition comprising a poly-alkyleneglycol is stablized against molecular degradation and viscosity loss at elevated temperatures by about 0.1 to about 10% by weight of an arylhydroquinone such as p-acetylphenylhydroquinone.
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