- Photoassisted catalytic cleavage of the C-F bond in pentafluorophenol with ZnO and the effect of operational parameters
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The photocatalytic cleavage of the C?F bond in pentafluorophenol (PFP) with ZnO using 254 and 365 nm UV light has been investigated under different conditions. The defluoridation was monitored using an ionometer with a fluoride ion selective electrode. The photocleavage was more effective under 254 nm than under 365 nm UV light. With 254 nm UV light, TiO2-P25, TiO 2 (anatase), ZnO, and ZrO2 photocatalyzed the deflouridation of PFP, whereas CdS, CdO, and SnO2 did not. The defluoridation is enhanced by the addition of oxidants such as KIO4, KClO3, (NH4)2S2O8, and KBrO3. The periodate ion is found to be the most efficient oxidant. The defluoridation intermediates were found to be tetrafluorodihydroxybenzene, trifluorotrihydroxybenzene, and tetrafluoroquinone. CSIRO 2007.
- Ravichandran, Lakshiminarasimhan,Selvam, Kaliyamoorthy,Swaminathan, Meenakshisundaram
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Read Online
- Polyoxometalate-based supramolecular porous frameworks with dual-active centers towards highly efficient synthesis of functionalized: P -benzoquinones
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Selective oxidation of substituted phenols is an ideal method for preparing functionalized p-benzoquinones (p-BQs), which serve as versatile raw materials for the synthesis of a variety of biologically active compounds. Herein, two new polyoxometalate-based supramolecular porous frameworks, K3(H2O)4[Cu(tza)2(H2O)]2[Cu(Htza)2(H2O)2][BW12O40]·6H2O (1) and H3K3(H2O)3[Cu(Htza)2(H2O)]3[SiW12O44]·14H2O (2) (Htza = tetrazol-1-ylacetic acid), were synthesized and structurally characterized by elemental analysis, infrared spectroscopy, thermal analysis, UV-vis diffuse reflectance spectroscopy, and single-crystal X-ray and powder diffraction. The single-crystal X-ray diffraction analysis indicates that both compounds possess unique petal-like twelve-nucleated Cu-organic units composed of triangular and hexagonal metal-organic loops. In 1, the Cu-organic units are isolated and [BW12O40]5- polyoxoanions are sandwiched between staggered adjacent triangular channels in the structure. However in 2, the Cu-organic units extend into a two-dimensional layered structure, and the [SiW12O44]12- polyoxoanions occupy the larger hexagonal channels in the stacked structure. Both compounds as heterogeneous catalysts can catalyze the selective oxidation of substituted phenols to high value-added p-BQs under mild conditions (60 °C) with TBHP as the oxidant, particularly in the oxidation of 2,3,6-trimethylphenol to 2,3,5-trimethyl-p-benzoquinone (TMBQ, key intermediate in vitamin E production). Within 8-10 min, the yield of TMBQ is close to 100%, and oxidant utilization efficiency is up to 94.2% for 1 and 90.9% for 2. The turnover frequencies of 1 and 2 are as high as 5000 and 4000 h-1, respectively. No obvious decrease in the yield of TMBQ was observed after five cycles, which indicates the excellent sustainability of both compounds. Our study of the catalytic mechanism suggests that there is a two-site synergetic effect: (i) the copper ion acts as the catalytic site of the homolytic radical pathway; and (ii) the polyoxoanion acts as the active center of the heterolytic oxygen atom transfer pathway. This journal is
- An, Haiyan,Chang, Shenzhen,Chen, Yanhong,Huang, Yaohui,Luo, Huiyun,Zhu, Qingshan
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p. 8591 - 8603
(2021/11/17)
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- Oxidative degradation of toxic organic pollutants by water soluble nonheme iron(iv)-oxo complexes of polydentate nitrogen donor ligands
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The ability of four mononuclear nonheme iron(iv)-oxo complexes supported by polydentate nitrogen donor ligands to degrade organic pollutants has been investigated. The water soluble iron(ii) complexes upon treatment with ceric ammonium nitrate (CAN) in aqueous solution are converted into the corresponding iron(iv)-oxo complexes. The hydrogen atom transfer (HAT) ability of iron(iv)-oxo species has been exploited for the oxidation of halogenated phenols and other toxic pollutants with weak X-H (X = C, O, S,etc.) bonds. The iron-oxo oxidants can oxidize chloro- and fluorophenols with moderate to high yields under stoichiometric as well as catalytic conditions. Furthermore, these oxidants perform selective oxidative degradation of several persistent organic pollutants (POPs) such as bisphenol A, nonylphenol, 2,4-D (2,4-dichlorophenoxyacetic acid) and gammaxene. This work demonstrates the utility of water soluble iron(iv)-oxo complexes as potential catalysts for the oxidative degradation of a wide range of toxic pollutants, and these oxidants could be considered as an alternative to conventional oxidation methods.
- Jana, Rahul Dev,Munshi, Sandip,Paine, Tapan Kanti
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p. 5590 - 5597
(2021/05/04)
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- 2, 3, 5, 6-tetrafluoro-7, 7', 8, 8'-tetracyanoquinodimethane and preparation method thereof
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The invention discloses 2, 3, 5, 6-tetrafluoro-7, 7', 8, 8'-tetracyanoquinodimethane and a preparation method thereof. The preparation method comprises diazotization: carrying out diazotization of a compound A and a compound B to obtain a compound C, reduction: reducing the compound C into a compound D, oxidation: oxidizing the compound D into a compound E, and condensation: condensing the compound E and malononitrile to obtain a compound F, wherein the compound F is 2, 3, 5, 6-tetrafluoro-7, 7', 8, 8'-tetracyanoquinodimethane and the compounds A, B, C, D, E and F are shown in the description. The preparation method has good environmental friendliness and a high yield of 80% or more, is simple and easy and is suitable for industrial production.
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- Reactivity of a Ru(iii)-hydroxo complex in substrate oxidation in water
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A mononuclear RuIII-OH complex oxidizes substrates such as hydroquinones in water through a pre-equilibrium process based on adduct formation by hydrogen bonding between the RuIII-OH complex and the substrates. The reaction mechanism switches from hydrogen atom transfer to electron transfer depending on the oxidation potential of substrates. This journal is
- Ohzu, Shingo,Ishizuka, Tomoya,Kotani, Hiroaki,Kojima, Takahiko
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supporting information
p. 15018 - 15021
(2015/02/19)
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- Catalytic defluorination of perfluorinated aromatics under oxidative conditions using N-bridged diiron phthalocyanine
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Carbon-fluorine bonds are the strongest single bonds in organic chemistry, making activation and cleavage usually associated with organometallic and reductive approaches particularly difficult. We describe here an efficient defluorination of poly- and perfluorinated aromatics under oxidative conditions catalyzed by the μ-nitrido diiron phthalocyanine complex [(Pc)Fe III(μ-N)FeIV(Pc)] under mild conditions (hydrogen peroxide as the oxidant, near-ambient temperatures). The reaction proceeds via the formation of a high-valent diiron phthalocyanine radical cation complex with fluoride axial ligands, [(Pc)(F)FeIV(μ-N)FeIV(F) (Pc+?)], which was isolated and characterized by UV-vis, EPR, 19F NMR, Fe K-edge EXAFS, XANES, and Kβ X-ray emission spectroscopy, ESI-MS, and electrochemical techniques. A wide range of per- and polyfluorinated aromatics (21 examples), including C6F6, C6F5CF3, C6F5CN, and C6F5NO2, were defluorinated with high conversions and high turnover numbers. [(Pc)FeIII(μ-N)Fe IV(Pc)] immobilized on a carbon support showed increased catalytic activity in heterogeneous defluorination in water, providing up to 4825 C-F cleavages per catalyst molecule. The μ-nitrido diiron structure is essential for the oxidative defluorination. Intramolecular competitive reactions using C6F3Cl3 and C6F3H 3 probes indicated preferential transformation of C-F bonds with respect to C-Cl and C-H bonds. On the basis of the available data, mechanistic issues of this unusual reactivity are discussed and a tentative mechanism of defluorination under oxidative conditions is proposed.
- Colomban, Cédric,Kudrik, Evgenij V.,Afanasiev, Pavel,Sorokin, Alexander B.
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supporting information
p. 11321 - 11330
(2014/11/07)
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- Synthesis of fluorine-containing 1,4-dioxa-2-azaspiro-[4.5]deca-2,6,9- trienes by reaction of polyfluorinated cyclohexa-2,5-dienones with nitrile oxides
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4-Pentafluorophenoxy-, 4-nitro-, and 4-chloropentafluorocyclohexa-2,5-dien- 1-ones and 3,4,5-tris-(pentafluorophenoxy)trifluorocyclohexa-2,5-dien-1-one react with some benzonitrile and acetonitrile oxides exclusively at the carbonyl group, leading to the formation of mixtures of diastereoisomeric fluorinated 1,4-dioxa-2-azaspiro[4.5]deca-2,6,9-trienes in good yield.
- Kovtonyuk, V. N.,Kobrina, L. S.,Gatilov, Yu. V.
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p. 783 - 787,5
(2020/08/31)
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- Aerobic oxidation of hydroquinone derivatives catalyzed by polymer-incarcerated platinum catalyst
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(Chemical Equation Presented) It's a lock-in! A remarkably wide substrate scope of hydroquinones are oxidized to quinones in high yields in a platinum-catalyzed process with as low as 0.05 mol% catalyst. The aerobic oxidation is catalyzed by platinum nanoclusters trapped in a styrene-based polymer network (see scheme, PI Pt=polymer-incarcerated nanoclusters). The catalyst could be reused at least 13 times without any loss of catalytic activity.
- Miyamura, Hiroyuki,Shiramizu, Mika,Matsubara, Ryosuke,Kobayashi, Shu
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supporting information; experimental part
p. 8093 - 8095
(2009/04/13)
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- o-fluoranil chemistry: Diels-Alder versus hetero-Diels-Alder cycloaddition
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(Chemical Equation Presented) The title quinone undergoes [4 + 2] cycloadditions in two ways, Diels-Alder on the ring and hetero-Diels-Alder by attack at the oxygens. The latter mode of reaction is strongly favored thermodynamically, but there is a kinetic bias favoring the normal Diels-Alder addition that often prevails, especially with cycloaddends that are not electron-rich.
- Lemal, David M.,Ramanathan, Sudharsanam,Shellito, John
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p. 3392 - 3396
(2008/09/21)
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- Chemical consequences of fluorine substitution. Part 4. Diels-Alder reactions of fluorinated p-benzoquinones with Dane's diene. Synthesis of fluorinated D-homosteroids
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Four fluorinated p-benzoquinones (2) have been reacted with Dane's diene (1) in Diels-Alder reactions and the formed fluorinated D-homosteroids were characterized. The number of products, their stereochemistry and stability depends on the fluorine substitution pattern of the corresponding fluorinated p-benzoquinones. If the p-benzoquinone (2) contains an unfluorinated double bond, this bond reacts faster with diene 1 yielding endo-products selectively. In contrast, [4+2]cycloadditions with 2,6-difluoro (2c) and 2,3,5,6-tetrafluorobenzoquinone (2d) gave the products with exo-orientation of the carbonyl part preferably.
- Essers, Michael,Haufe, Guenter
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p. 2719 - 2728
(2007/10/03)
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- Activation of electron transfer reduction of p-benzoquinone derivatives by intermolecular regioselective hydrogen bond formation
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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
- Fukuzumi, Shunichi,Kitaguchi, Hironori,Suenobu, Tomoyoshi,Ogo, Seiji
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p. 1984 - 1985
(2007/10/03)
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- Photoinduced electron transfer between acenaphthylene and 1,4-benzoquinones. Formation of dimers of acenaphthylene and 1 : 1-adducts and effect of excitation mode on reactivity of the charge-transfer complexes
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Photochemical reactions of acenaphthylene (ACN) with 1,4-benzoquinones (BQs) of varying reduction potentials in solution have been investigated in order to determine final products and quantum yields of the reactions and to get an insight into the factors
- Haga, Naoki,Takayanagi, Hiroaki,Tokumaru, Katsumi
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p. 734 - 745
(2007/10/03)
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- Polyfluorinated arylnitramines
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N-methyl- and N-butylperfluoroarylamines are transformed by HNO3 into N-nitro-N-methyl- and N-nitro-N-butylperfluoroarylamines. These reactions were used to synthesise N-nitro-N-methylpentafluoroaniline and its p-CF3, -CN, -C6F5 substituted derivatives, N-nitro-N-methylperfluoro-2,4-xylidine, N-nitro-N-methyl-4-aminotetrafluoropyridine, N-nitro-N-methyl-5-aminoperfluoroindane, N-nitro-N-methyl-2-aminoheptafluoronaphthalene, 4,4′-bis(N-nitro-N-methylamino)octafluorobiphenyl from 4,4′-bis(N-methylamino)octafluorobiphenyl, N-nitro-N-n-butylpentafluoroaniline, N-nitro-N-n-butylperfluoro-p-toluidine, N-nitro-N-n-butyl-4-aminotetrafluoropyridine and N-nitro-bis(perfluoro-p-tolyl)amine. Tetrafluoro-p-benzoquinone and heptafluoro-p-toluquinol were obtained from N-methylpentafluoroaniline and N-methylperfluoro-p-toluidine, respectively, under the action of a mixture of HNO3 and H2SO4. The X-ray crystal structure of N-nitro-N-methylperfluoro-p-toluidine was determined.
- Platonov,Haas,Schelvis,Lieb,Dvornikova,Osina,Gatilov, Yu.V.
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p. 131 - 139
(2007/10/03)
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- Conversion of pentahalogenated phenols by microperoxidase-8/H2O2 to benzoquinone-type products
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This study reports the microperoxidase-8 (MP8)/H2O2-catalyzed dehalogenation of pentafluorophenol and pentachlorophenol, compounds whose toxic effects and persistence in the environment are well documented. The primary products of this dehalogenation reaction appear to be the corresponding tetrahalo-p-benzoquinones. Under the conditions used, the fluorinated phenol and its intermediate products are more susceptible to degradation than the corresponding chlorinated analogue and its products. The main degradation products of tetrachloro-p-benzoquinone and tetrafluoro-p- benzoquinone were identified as trichlorohydroxyp-benzoquinone and trifluorohydroxy-p-benzoquinone, respectively. This secondary conversion of tetrafluoro-p-benzoquinone and tetrachloro-p-benzoquinone was not mediated by MP8, but was driven by H2O2. Evidence is presented for a mechanism where H2O2 molecules and not hydroxide anions are the reactive nucleophilic species attacking the tetrahalo-p-benzoquinones. In addition to the formation of the trihalohydroxy-p-benzoquinones, the formation of adducts of the tetrahalo-p-benzoquinone products with ethanol, present in the incubation medium, was observed. The adduct from the reaction of tetrachloro-p- benzoquinone with ethanol was isolated and identified as trichloroethoxyquinone. Thus, the present paper describes a system in which the formation of tetrahalo-p-benzoquinone-type products by an oxidative heme- based catalyst could be unequivocally demonstrated.
- Osman, Ahmed M.,Posthumus, Maarten A.,Veeger, Cees,Van Bladeren, Peter J.,Laane, Colja,Rietjens, Ivonne M.C.M.
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p. 1319 - 1325
(2007/10/03)
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- Oxidation of Tetrafluorobenzene Derivatives with Cerium(IV) Perchlorate
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Mechanisms for oxidation of 2,3,5,6-tetrafluoro derivatives of hydroquinone, phenol, and aniline with cerium(IV) ions are poroposed on the basis of experimantal data and AMI calculations of the electron and spin densities of corresponding radicals and radical cations and enthalpies of formation of possible intermediate products. Factors preventing oxidation of 2,3,5,6-tetrafluoroanisole with Ce(IV) ions are discussed.
- Dziegiec,Grzejdziak
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p. 116 - 119
(2007/10/03)
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- Electrophilic oxygenation with XeF2 - H2O in hydrogen fluoride, Part 2. Electrophilic oxygenation of pentafluorobenzene derivatives C6F5X
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Electrophilic oxygenation of polyfluorobenzenes C6F5X (X = F, Cl, Br, H, CF3, NH3+, NMe3+, OH and OCH2CF3) with XeF2 and H2O in HF leads to the formation of polyfluorinated 1,4-cyclohexadienones. Pentafluoroiodobenzene is converted into C6F5IF2 and C6F5IF4, whereas [C6F5N2]+ [NbF6]- is unreactive towards this new type of electrophilic oxygenation.
- Frohn,Bardin
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p. 1015 - 1021
(2007/10/03)
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- Photoinduced Electron Transfer in Pinacol Cleavage with Quinones via Highly Labile Cation Radicals. Direct Comparison of Charge-Transfer Excitation and Photosensitization
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Benzopinacol and related diphenylethane-like donors (D) form electron donor-acceptor (EDA) complexes with chloranil and similar benzoquinones (A), in which the deliberate irradiation of the charge-transfer absorption band (hνCT) leads to oxidative cleavage (retropinacol) via electron transfer.Photosensitization by excitation of the ?-?* band of chloranil and diffusive quenching also effects the C-C bond cleavage of the same donors.The photoefficiencies of both photochemical processes are quantitatively compared with respect to the lifetimes of the pinacol cation radicals (D+ radical), as determined by the competition from back electron transfer and diffusion.These photoinduced processes are considered in the context of electron-transfer for an equivalent thermal reaction which occurs in the dark with high-potential quinones and electron-rich pinacols.
- Perrier, Serge,Sankararaman, Seth,Kochi, Jay K.
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p. 825 - 837
(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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- HIGHLY STEREOSPECIFIC THERMOLYSIS OF SPIROOXETANES CONTAINING TETRAHALOGENATED 1,4-BENZOQUINONE MOIETIES
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Thermolysis of cis- and trans-spirooxetanes (1) proceeded with 94-100percent retention of stereochemistry to give stilbene (2) and quinones (3).Important role of a concerted pathway was assumed.
- Oshima, Takumi,Nagai, Toshikazu
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p. 3443 - 3444
(2007/10/02)
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- N-(POLYFLUOROARYL)-HIDROXYLAMINES. SYNTHESIS AND PROPERTIES
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Fluorine-containing N-arylhydroxylamines have been obtained by the reaction of hydroxylamine or its N- and O-derivatives on polyfluorinated benzenes and pentafluoropyridine.The influence of fluorine atoms on the reactivity of hydroxylamino group has been investigated.The reaction of N-polyflouroarylhydroxylamines with aldehydes has been shown not to occur, whereas their reaction with nitrosobenzenes leads to azoxybenzenes and with Lewis acids leads to corresponding nitrosobenzenes, azoxybenzenes and anilines.The action of acids on 2,3,5,6-tetrafluorophenylhydroxylamine leads to the acid-catalyzed rearrangement of the latter into 4-amino-2,3,5,6-tetrafluorophenol.C,N-Diarylnitrones have been obtained by the oxidation with MnO2 of fluorine-containing arylhydroxylamines possessing the CH-fragment in an α-position.
- Miller, A.O.,Furin, G. G.
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p. 247 - 272
(2007/10/02)
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- Electron Affinities of Di- and Tetracyanoethylene and Cyanobenzenes Based on Measurements of Gas-Phase Electron-Transfer Equilibria
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The electron affinities of tetracyanoethylene, trans-1,2-dicyanoethylene, and eleven substituted benzonitriles as well as two naphthonitriles were determined by measurement of the electron-transfer equilibria A-+B=A+B- with a pulsed electron high ion source pressure mass spectrometer.Rate constants for exothermic electron transfer involving the cyano compounds were found to be near unit collision efficiency.The EA (tetracyanoethylene)=3.17 eV obtained in the present work is considerably higher than the 2.3 eV photodetachment value of Palmer and Lyons.The electron affinities of benzene and benzonitrile substituted by CN, CHO, and NO2 increase in the given order, while the order for nitrobenzene is CHO, CN, NO2.This reversal of order is explained on the basis of a larger attenuation of the ?-withdrawing effect relative to the field effect of substituents when the electron density in the ?* single-electron orbital is decreased.
- Chowdhury, Swapan,Kebarle, Paul
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p. 5453 - 5459
(2007/10/02)
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- INTERACTION OF PENTAFLUOROPHENOL WITH LEAD TETRAACETATE IN ACIDS
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The ability of polyfluorinated hydroxyaromatic compounds to be oxidised by radical and ionic mechanisms is discussed.Oxidation of pentafluorophenol by lead tetraacetate in hydrogen fluoride and trifluoroacetic acid gave the products of a reaction proceeding by an ionic mechanism - hexafluorocyclohexa-2,5-dienone and trifluoroacetoxydienones respectively.
- Kovtonyuk, V.N.,Kobrina, L.S.,Yakobson, G.G.
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- AROMATIC FLUORINE DERIVATIVES. C. REACTIONS OF PENTAFLUOROPHENOL WITH VANADIUM, NIOBIUM, AND ANTIMONY FLUORIDES AND XENON DIFLUORIDE
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Pentafluorophenol reacts with vanadium fluorides and xenon difluoride giving perfluoro-2,5-cyclohexadien-1-one and the products from dimerization of the pentafluorophenoxyl radical, i.e., perfluoro-6-phenoxy-2,4-cyclohexadien-1-one, perfluoro-4-phenoxy-2,5-cyclohexadien-1-one, and perfluoro-2-phenoxy-2,5-cyclohexadien-1-one.Antimony and niobium pentafluorides give stable complexes or the corresponding pentafluorophenolates with pentafluorophenol.
- Avramenko, A. A.,Bardin, V. V.,Karelin, A. I.,Krasil'nikov, V. A.,Tushin, P. P.,et. all
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p. 746 - 749
(2007/10/02)
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- New Routes to Hexafluorocyclopentadiene and Related Compounds
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Hexafluorocyclopentadiene (1) has been synthesized in two steps from pentafluorophenol (2) by fluorination followed by flash vacuum pyrolysis of the resulting hexafluorocyclohexadienones 3 and 4.Similar pyrolysis of 6-chloropentafluorocyclohexadienone (13) gave an equilibrium mixture of 1- and 2-chloropentafluorocyclopentadiene (15 and 16), presumably via the 5-chloro isomer.Flash vacuum pyrolysis of tetrafluoro-o-benzoquinone 17 yielded tetrafluorocyclopentadienone (20).Hexafluorocyclopentadiene was also prepared via a ring-expansion route which entailed cycloaddition (accompanied by rearrangement) of bromotrifluoroethylene to tetrafluorocyclopropene followed by reductive debromofluorination.
- Soelch, Richard R.,Mauer, George W.,Lemal, David M.
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p. 5845 - 5852
(2007/10/02)
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- Phosphorescence exhibiting materials for optically pumped lasers
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Chemical compounds resulting from the mixing of organosilanes and quinones in the presence of di-tert-butyl peroxide as a sensitizer, exhibit strong blue phosphorescence. These compounds are highly resistant to deterioration by heat and UV irradiation. The unique feature of enhanced phosphorescence quantum efficiency at high temperature makes these systems most suitable for solar pumped lasers which usually will operate at relatively high temperature.
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