- Electron Dissociative Attachment to NF2 Radicals
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Measurements of discharge current in an electron beam sustained-discharge device have been used to determine the dissociative attachment rate constant of electrons to NF2 radicals.This was done by measuring the relative rate of electron attachment to NF2 compared to dilute molecular chlorine in a nitrogen buffer in separate experiments in the same device.A comparison of the steady-state current measured for these two different mixtures at identical total pressures and applied electric fields provides a relative measurement for the rate of disappearance of electrons.Since the attachment rate constant with molecular chlorine is well-known, rate constants for the fluoride radical could be determined.Values near 1.5 x 1E-9 cm3/s for average electron energies near 1 eV were obtained.
- Trainor, Daniel W.
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- Unexpected Hydrated Electron Source for Preparative Visible-Light Driven Photoredox Catalysis
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The hydrated electron is experiencing a renaissance as a superreductant in lab-scale reductions driven by light, both for the degradation of recalcitrant pollutants and for challenging chemical reactions. However, examples for its sustainable generation under mild conditions are scarce. By combining a water-soluble Ir catalyst with unique photochemical properties and an inexpensive diode laser as light source, we produce hydrated electrons through a two-photon mechanism previously thought to be unimportant for laboratory applications. Adding cheap sacrificial donors turns our new hydrated electron source into a catalytic cycle operating in pure water over a wide pH range. Not only is that catalytic system capable of detoxifying a chlorinated model compound with turnover numbers of up to 200, but it can also be employed for two novel hydrated electron reactions, namely, the decomposition of quaternary ammonium compounds and the conversion of trifluoromethyl to difluoromethyl groups.
- Kerzig, Christoph,Guo, Xingwei,Wenger, Oliver S.
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- Electron affinities and gas-phase acidities of organogermanium and organotin compounds
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The electron affinities have been measured for trimethylgermanium and trimethyltin radicals as 31.9 ± 0.7 and 39.2 ± 1.5 kcal/mol, respectively, using electron photodetachment spectroscopy. The acidities (ΔH°acid) for the corresponding hydrides
- Brinkman, Elizabeth A.,Salomon, Karen,Tumas, William,Brauman, John I.
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- Negative-ion mass spectrometric study of ion-pair formation in the vacuum ultraviolet. III. SF6 -> F- + SF5+
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Ion-pair formation from photoexcitation of SF6 has been studied by negative-ion mass spectrometry using synchrotron radiation in the 11.27-31.0 eV photon energy range.Negative ions F-, SF6-, and SF5- have been observed.The appearance energy of the F- ion is about 1 eV higher than the thermochemical threshold for the formation of the pair of the ground state ions F- (1Sg) and SF5+ (X1A1).The peak features observed in the F- efficiency curve are interpreted as resulting from transitions to neutral excited states with the 1T1u symmetry which effectively couple with ion-pair states through avoided potential surface crossings.The peaks assigned to diffuse Rydberg states are distinctively enhanced in the F- efficiency curve, probably because of large transition probabilities from the dissociative Rydberg states to the ion-pair states.In contrast, the excited states of valence type autoionize in a short period and have quite small branching to the ion-pair channel.Consequently, the corresponding peaks are markedly suppressed in the F- spectrum.Assignments of the peak features in the previous photoabsorption spectra are also performed by using the term values for related Rydberg and virtual valence orbitals.Other negative ions observed, SF6- and SF5-, are produced by resonance capture of low energy electrons emitted by photoionization of the parent molecules, and are not of major concern of the present study.
- Mitsuke, Koichiro,Suzuki, Shinzo,Imamura, Takashi,Koyano, Inosuke
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- Fluoride Affinities of Perfluorobenzenes C6F5X. Meisenheimer Complexes in the Gas Phase and Solution
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Measurements of gas phase fluoride transfer equilibria lead to ΔGo and ΔHo for the reaction F- + C6F5X = where the substituents X of the perfluorobenzenes are F, H, CF3, COCH3, CN, and NO2.The relative energy changes are found to lead to an approximately linear correlation with the electron affinities of C6F5X.The gas-phase ΔGo and ΔHo data are used in combination with rate measurements in solution from the literature for a comparison of the reaction coordinates in the gas phase and solution and for determinations of the solvation energy of the transition state occuring in solution.
- Dillow, Glen W.,Kebarle, Paul
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- Reactions of highly excited atoms with molecules A* *+BC→A++B+C-
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Reactions of highly excited atoms (A**) with molecules (BC) A**+BC→A++B+C-, (1) are studied. It is theoretically shown that the cross section for (1) can be approximately expressed in terms of that for dissociative attachment of electrons to molecules BC, namely, e+BC→B+C-. The rate constants and the angular distributions of the products for some reactions including Kr**+CCl4→Kr + + CCl3+Cl-, (2) are predicted. The rate constant for reaction (2) is found to be of the order of the magnitude 10 -7 cm3/sec. Together with the results of the previous papers (M. Matsuzawa: J. chem. Phys. 55 (1971) 2685; J. Phys. Soc. Japan 32 (1972) 1088) it is pointed out that the measurements of reactions of highly excited atoms with molecules give useful information on the inelastic scattering of a slow electron by the molecules.
- Matsuzawa, Michio
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- Synthesis of nano-sized lanthanum oxyfluoride powders by mechanochemical processing
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Lanthanum oxide (La2O3) was subjected to grinding with polytetrafluoroethylene (PTFE, (CF2CF2)n) in air using a planetary mill followed by thermal treatment to synthesize lanthanum oxyfluoride ultra-fine particles. The grinding operation causes mechanochemical (MC) reaction between the two materials. The MC reaction is almost finished by 240 min, and the products ground for 240 min or more are composed of LaOF, amorphous La(CO3)F and amorphous carbon (C). Heating this MC reaction product at 600°C enables us to eliminate amorphous C and decompose La(CO3)F into LaOF, so that pure LaOF material can be obtained as the final product. The average particle size of the final product (purified LaOF) is around 10 nm.
- Lee, Jaeryeong,Zhang, Qiwu,Saito, Fumio
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- Intentional hydrolysis to overcome the hydrolysis problem: Detection of Ce(iv) by producing oxidase-like nanozymes with F-
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Polyvalent metal ions are susceptible to hydrolysis, making their reproducible detection by sensors and biosensors difficult. We herein turned this disadvantage into an advantage to develop a high selectivity colorimetric method for detecting Ce(iv) by intentionally hydrolyzing it through heating, where subsequent addition of F- recovered the activity, allowing a detection limit of 3.8 μM Ce(iv).
- Wang, Yawen,Yang, Jianzhong,Zhao, Yilin,Liu, Juewen
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- Synthesis of [18F]Fluoroform with High Molar Activity
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Fluoroform is an interesting motif for the isotopologue labelling of biologically active compounds with fluorine-18 for PET imaging. However, so far the building block [18F]fluoroform and consequently the [18F]trifluoromethylated products suffered from low molar activities ranging from 0.1 to 30 GBq/μmol due to isotopic dilution under the strongly basic standard radiofluorination conditions. In this article the synthesis of high molar activity [18F]fluoroform is described. By implementing a recently reported novel radiofluorination reagent, [18F]triflyl fluoride, the concentration of base-cryptand complex in the reaction could be reduced 100-fold compared to standard radiofluorination conditions and molar activities close to 100 GBq/μmol (at end of [18F]fluoroform synthesis) could be obtained, enabling the imaging of low density receptors. Furthermore, an automated procedure was developed on the commercially available NEPTIS perform synthesizer to provide access of high molar activity [18F]fluoroform to other PET centres.
- Pees, Anna,Tadino, Vincent,Vosjan, Maria J. W. D.,Vugts, Danielle J.,Windhorst, Albert D.
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- Nanopore enriched hollow carbon nitride nanospheres with extremely high visible-light photocatalytic activity in the degradation of aqueous contaminants of emerging concern
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Construction of highly efficient hollow nanosphere photocatalytic systems has been strongly attracting the attention of researchers. In the present work, nanopore enriched hollow carbon nitride nanospheres (HCNNSs) with a smaller particle size (200 nm) and a thinner shell thickness (40 nm) are successfully fabricated by a silica-nanocasting strategy. Such unique structures possess many advantages such as large BET surface area (122 m2 g-1), high light-harvesting ability, fast charge separation and transfer efficiency, plentiful exposed active sites and enhanced oxidation ability of photogenerated holes (h+VB). Therefore, HCNNSs in smaller sizes (HCNNS-200) exhibit extremely excellent visible-light photocatalytic efficiency towards the degradation of contaminants of emerging concern, e.g. levofloxacin (LEVO), in comparison with bulk g-C3N4 and HCNNSs in larger sizes (HCNNS-500). And it takes less than 10 min to finish the degradation of LEVO. The experimental results including those from indirect chemical probing, electron spin resonance, ion chromatography and high performance liquid chromatography-mass spectrometry confirm that h+VB and O2- are the active species that are responsible for the mineralization of LEVO to NO3-, F-, H2O and CO2 under visible-light irradiation. Additionally, the degradation pathway of LEVO in the HCNNS-200 photocatalytic system is also proposed. It is expected that HCNNS-200 can be used as a promising photocatalyst for environmental remediation.
- Yang, Yuxin,Hu, An,Wang, Xinyue,Meng, Jiaqi,Guo, Yihang,Huo, Mingxin,Zhu, Suiyi
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p. 355 - 365
(2019/01/28)
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- Rate constants and C–C bond scission ratios for hydrolysis of 2,2,3-trifluoro-3-(trifluoromethyl)oxirane determined by means of a closed-circulation reactor
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The hydrolysis rate constant of 2,2,2-trifluoro-3-(trifluoromethyl)oxirane (hexafluoropropene oxide; HFPO), a versatile precursor of fluorinated chemicals, was determined at 279–307 K, and the rate of hydrolysis was used to estimate the tropospheric lifetime of HFPO with respect to hydrolysis in clouds or uptake by the ocean. The low solubility of HFPO in water made it difficult to determine the hydrolysis rate constant because of mass-transfer limitation between the gas and liquid. A closed-circulation reactor was used to measure the rate of decrease of the partial pressure of HFPO while an HFPO-air mixture flowed over a stirred test solution under various experimental conditions. The rate of hydrolysis increased as the OH? concentration increased in an aqueous NaOH solution but was almost independent of the H2SO4 concentration in aqueous H2SO4 solutions. Much scissioning of C–C bonds in HFPO produced carbon monoxide and trifluoroacetate in aqueous NaOH, but similar scissioning did not in water or aqueous H2SO4. The first-order rate constant for the pH-independent hydrolysis (kwater in s?1), the bimolecular rate constant for the hydroxide-catalyzed hydrolysis, and the temperature dependence of these parameters were estimated by simultaneously fitting equations based on a two-film model to the time series of HFPO partial pressures under different experimental conditions. The equations included the rate constants as common parameters. The product of kwater and the Henry's law constant, KH (M Pa?1), at a temperature of T (K) was determined to be kwater × KH = 3.7 × 10?11 exp[?3300 × (T?1 ? 1/298.2)]. The tropospheric lifetime of HFPO estimated using this equation indicates that removal of HFPO via hydrolysis in clouds is probably not a substantial sink of HFPO and suggests that, in the absence of other atmospheric sinks of HFPO, hydrolysis of HFPO in the ocean would be the major sink of HFPO.
- Kutsuna, Shuzo
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p. 109 - 118
(2018/05/04)
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- Radiofluorination of a NHC-PF5 adduct: Toward new probes for 18F PET imaging
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The radiofluorination of N-heterocyclic carbene (NHC) phosphorus(v) fluoride adducts has been investigated. The results show that the IMe-PF5 derivative (IMe = 1,3-dimethylimidazol-2-ylidene) undergoes a Lewis acid promoted 18F-19F isotopic exchange. The resulting radiofluorinated probe is remarkably resistant to hydrolysis both in vitro as well as in vivo.
- Vabre, Boris,Chansaenpak, Kantapat,Wang, Mengzhe,Wang, Hui,Li, Zibo,Gabba?, Fran?ois P.
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supporting information
p. 8657 - 8659
(2017/08/09)
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- Enhancing the anion affinity of urea-based receptors with a Ru(terpy) 22+ chromophore
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Covalent linking of a Ru(terpy)22+ substituent improves recognition and sensing properties of the urea subunit toward anions. Urea's anion affinity is enhanced by the electrostatic attraction exerted by the RuII cation and by the electron-withdrawing effect exerted by the entire polypyridine-metal complex. Such an enhancement of the anion affinity, which results from the combination of a through-space and a through-bond effect, is greater than that exerted by the classical neutral electron-withdrawing substituent nitrophenyl. Small yet significant modifications of π-π* and MLCT bands of the Ru(terpy)22+ chromophore, detected through UV-vis spectrophotometric titrations, allowed the determination of the constants for the formation of receptor-anion H-bond complexes in diluted MeCN solution. On 1H NMR titration experiments, carried out under more concentrated conditions, the interaction of a second Cl- ion was observed, taking place through an outer-sphere mechanism. The Ru(terpy) 22+ substituent favors the deprotonation of a urea N-H fragment on addition of a second equivalent of fluoride, with formation of HF2-.
- Baggi, Giorgio,Boiocchi, Massimo,Ciarrocchi, Carlo,Fabbrizzi, Luigi
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p. 5273 - 5283
(2013/06/26)
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- Neutron and β/γ radiolysis of water up to supercritical conditions. 2. SF6 as a scavenger for hydrated electron
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SF6 has been used as a specific scavenger to investigate the β/γ radiolysis yield of hydrated electrons in pressurized high temperature sub- and supercritical water. SF6 is thermally stable in supercritical water, and each scavenging reaction is known to produce six fluoride ions, which can be readily measured using a fluoride-selective electrode. Problems in the application of this method are described, including buildup of acid product and chain reduction of SF6 in the presence of organic ·H and ·OH radical scavengers. Ultimately we find that the combination of SF6 and phenol in neutral solution gives reliable results in supercritical water, because the protons and fluoride ions remain associated as HF molecules. The β/γ yields in supercritical water are similar to previous measurements using N2O scavenger.
- Haygarth, Kyle,Bartels, David M.
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p. 7479 - 7484
(2010/10/03)
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- Sulfuric acid breakdown of fluorite in the presence of silica
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We study the reaction of CaF2 with concentrated sulfuric acid in the presence of silica at 120 and 140°C using fluorite mineral, fluorite concentrate, and mica-fluorite ore samples. When steam is fed to the reaction mixture, fluorosilicic acid
- Krysenko,Gordienko,Epov
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p. 1876 - 1879
(2010/05/01)
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- Electron transfer reactions of peroxydisulfate and fluoroxysulfate reactions with the cyanide complexes M(CN)n4- (M=Fe(II), Ru(II), Os(II), Mo(IV), and W(IV))
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The stoichiometry and the kinetics of oxidation of the cyanide complexes M(CN)n4- (M = Fe(II), Ru(II), Os(II), Mo(IV), and W(IV)) by the peroxydisulfate ion, S2O82-, and by the much more strongly oxidizing fluoroxysulfate ion, SO4F-, were studied in aqueous solutions containing Li+. Reactions of S 2O82- with -M(CN)4- are known to be strongly catalyzed by Li+ and other alkali metal ions, and this applies also to the corresponding reactions of SO4F -. The primary reactions of S2O82- and SO4F- have both been found to be one-electron processes in which the equally strong O-O and O-F bonds are broken. The primary reaction of S2O82- consists of a single step yielding M(CN)n3-, SO4-, and SO 42-, whereas the primary reaction of SO4F - comprises two parallel one-electron steps, one leading to M(CN)n3-, SO4-, and F- and the other yielding M(CN)n-12- CN-, SO 4- and F-. The relationship between the rate constants and the standard free energies of reaction for the Li +-catalyzed reactions of SO4F- and S 2O82 with M(CN)n4-, and for the uncatalyzed reactions of S2O82- with bipyridyl and phenanthroline complexes MLn2+ (M = Fe(II), Ru(II), and Os(II)) studied previously, suggests that the intrinsic barrier for all three sets of reactions is similar, i.e., unaffected by the Li+ catalysis, and that the electron transfer and the breakage of the O-O and O-F bonds are concerted processes.
- Klaening, Ulrik,Byberg, Jorgen R.,Daasbjerg, Kim,Sehested, Knud,Appelman, Evan H.
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p. 1419 - 1425
(2008/10/09)
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- Kinetics of sulfur oxide, sulfur fluoride, and sulfur oxyfluoride anions with atomic species at 298 and 500 K
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The rate constants and product-ion branching ratios for the reactions of sulfur dioxide (SO2-), sulfur fluoride (SF n-), and sulfur oxyfluoride anions (SOxF y-) with H, H2, N, N2, NO, and O have been measured in a selected-ion flow tube (SIFT). H atoms were generated through a microwave discharge on a H2/He mixture, whereas O atoms were created via N atoms titrated with NO, where the N had been created by a microwave discharge on N2. None of the ions reacted with H 2, N2 or NO; thus, the rate constants are -12 cm3 s-1. SOxFy - ions react with H by only fluorine-atom abstraction to form HF at 298 and 500 K. Successive F-atom removal does not occur at either temperature, and the rate constants show no temperature dependence over this limited range. SO2- and F- undergo associative detachment with H to form a neutral molecule and an electron. Theoretical calculations of the structures and energetics of HSO2- isomers were performed and showed that structural differences between the ionic and neutral HSO 2 species can account for at least part of the reactivity limitations in the SO2- + H reaction. All of the SOxF y- ions react with O; however, only SO2 - reacts with both N and O. SOxFy- reactions with N (SO2- excluded) have a rate constant limit of -11 cm3 s-1. The rate constants for the SOxFy- reactions with H and O are ≤25% of the collision rate constant, as seen previously in the reactions of these ions with O3, consistent with a kinetic bottleneck limiting the reactivity. The only exceptions are the reactions of SO2 - with N and O, which are much more efficient. Three pathways were observed with O atoms: F-atom exchange in the reactant ion, F- exchange in the reactant ion, and charge transfer to the O atom. No associative detachment was observed in the N- and O-atom reactions.
- Midey, Anthony J.,Viggian
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p. 1852 - 1859
(2008/10/09)
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- Modification of an NF3 film by sub-excitation electrons
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By applying the IRAS technique (infrared-absorption-reflection spectroscopy) and electron stimulated desorption (ESD) of negative ions we demonstrate that a 10 monolayer (ML) film of NF3 is degraded in the course of low-energy electron irradiation in the range 0-5 eV which is far below the electronic excitation of NF3. Degradation is accompanied by the desorption of F- fragment ions from the film and formation of NF2 radicals and N2F4 molecules in the film. The energy dependence of the degradation cross-section follows that for resonant (dissociative) electron attachment in the low-energy region (≈0-5eV) and increases above 6 eV. We therefore identify (dissociative) electron capture at low energy as the only initial reaction responsible for the chemical changes in the NF3 film.
- Tegeder, Petra,Illenberger, Eugen
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p. 401 - 406
(2008/10/08)
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- Kinetics and Mechanism of Hydrolysis of Hexacoordinate Fluorosilicates in the Presence of Ammonium
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The hydrolysis kinetics of hexacoordinate silicon fluoro complexes - constituents of fluorosilicic acids - at various ammonium concentrations was studied in the temperature range 278.2-298.0 K. The observed reaction rate coefficients, catalysis coefficients KNH4+ , and activation parameters of hydrolysis involving NH4+ were calculated. A possible mechanism of the promoting influence of NH4+ was suggested, which implies that the weakening of Si-F bonds results from an electron-density shift towards the cation because of the formation of an ion associate with the silicon fluoro complex, which presumably incorporates water molecules.
- Murashkevich,Zharskii,Poloiko
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- Radical-mediated degradation mechanisms of tribromo- and other trihalogenated acetic acids in oxygen-free solutions as studied by radiation chemistry methods
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.CBr2CO2- and .CCl2CO2- radicals, generated upon one electron reduction of tribromo- and trichloroacetic acids and .CF2CO2- radicals produced from difluoroacetic acid by reaction with .OH, exhibit optical absorptions in the UV with λmax at 290 nm (ε = 2580 dm3 mol-1 cim-1), 330 nm (ε = 3000 dm3 mol-1 cm-1) and 310 nm (ε ≈ 660 dm3 mol-1 cm-1), respectively. Mechanistically, the present report focuses on the free-radical-induced degradation of tribromoacetic acid. Absolute rate constants have been determined for the reactions of CBr3CO2- with eaq-, H., CO2. , .CH2OH, CH3.CHOH, (CH3)2.COH and .CH3 radicals to be k = 1.8 × 1010, 1.5 × 1010, 2.8 × 109, 1.6 × 109, 2.3 × 109, 3.0 × 109 and 3.0 × 107 dm3 mol-1 s-1, respectively. The major fate of .CBr2CO2- is self-termination to yield tetrabromosuccinic acid which, however, is unstable and thermally decomposes to HBr, CO2 and tribromoacrylic acid. Dibromofumaric acid, dibromomaleic acid and carbon monoxide were found as minor secondary products, formation of which is explained by a small yield of reductive decomposition of the transient tetrabromosuccinic acid. A complete and mechanistically satisfying material balance is provided for several systems in which CBr3CO2- has been degraded via a variety of radicals under various conditions. .OH Radicals do not react directly with CBr3CO2-. They have been shown, however, to contribute indirectly to the degradation of this acid via their reaction with reductively liberated bromide ions. The Br. atoms formed in this process are considered to abstract a bromine atom from CBr3CO2- or oxidize the carboxyl function in a one-electron transfer process. The formation of free Br. atoms has been recognized by pulse radiolysis through their conjugate dimer radical anions Br2.-. With respect to the other trihalogenated acids it is noteworthy that CCl3CO2- is efficiently reduced by CO2.- radicals and that CF3CO2- exhibits a high stability toward γ-irradiation and practically resists any reductive attack.
- Fliount, Roman,Makogon, Oksana,Guldi, Dirk M.,Asmus, Klaus-Dieter
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p. 1535 - 1545
(2007/10/03)
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- Kinetics of the Reactions of F- with CF3Br and CF3I as a Function of Temperature, Kinetic Energy, Internal Temperature, and Pressure
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The reactions of F- with CF3Br and CF3I have been studied at several temperatures as functions of pressure and ion-neutral average center-of-mass kinetic energy (cm>).Rate constants and product branching fractions were measured by using a variable temperature-selected ion flow drift tube apparatus.Both title reactions involve two product pathway: displacement and association, the latter being the major channel under most experimental conditions.The rate constants for displacement are governed by total energy, regardless of the relative contributions by translational and internal energy, indicating that the displacement reactions behave statistically.In contrast, the rate constants for association depend strongly on the internal energy of CF3X (rotations and vibrations) compared with the relatively weak effect of translational collision energy.For CF3Br the rate constants for the association channel increase with increasing pressure while those for displacement are independent of pressure, indicating that the additional reactivity leading to more association at higher pressure appears not to compete with the displacement pathway.This lack of competition may be the result of two different reaction intermediates.The more efficient CF3I reaction is at or near the high-pressure limit for association, showing no pressure dependence in both the association and displacement channels.Therefore, there appears to be no competition between these channels for CF3I as well, but the data are less definitive in this case.
- Morris, Robert A.,Viggiano, A. A.
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p. 3740 - 3746
(2007/10/02)
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- A comprehensive view of the gas-phase reaction of fluoride ions and acetic acid derivatives
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The gas-phase reaction of F- with several acetic acid derivatives (MeCOX) is shown to proceed primarily by proton abstraction in the collision complex, rather than nucleophilic displacement, leading to the facile formation of FHX- or CH2CFO-.
- Riveros, Jose M.
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p. 773 - 774
(2007/10/02)
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- Catalytic effect of Na+ and Li+ cations on ligand substitution reactions in the methoxytrifluoroborate anion
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The kinetics of fluoride ion substitution in methoxytrifluoroborate have been studied in the presence of alkali metal cations. The process sensitivity to cationic catalysts has been shown to increase in media containing high methanol concentrations. It has also been established that decreasing the cationic radius in the series K+ → Na+ → Li+ leads to a stronger catalytic effect. Conclusions have been drawn concerning the predominance of contact (tight) ion pairs.
- Kharchenko,Plakhotnik,Parkhomenko,Kopanev,Sokolov
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p. 821 - 824
(2008/10/08)
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- Associative and dissociative electron attachment by SF6 and SF5Cl
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Electron attachment by SF6 and SF5Cl in the energy range 0-20 eV has been studied in a beam experiment at room temperature.At low energies ( ca. 0 eV) electron attachment to SF6 yields the well known parent anion SF6-* (associative attachment) and SF5- (dissociative attachment), while other negative ion fragments (F-, F2-, SF2-, SF3-, and SF4-) are generated with comparably low cross sections from various resonances at higher energies.In contrast to that, negative ion formation in SF5Cl is dominated by dissociative channels (F-, Cl-, FCl-, and SF5-) and only a weak SF5Cl- signal is observed.A time-of-flight analysis of the ionic fragments reveals that the decomposition of all resonances is characterized by a low translational excess energy relase indicating effective energy randomization in the parent ion prior to dissociation.The present results are compared with negative ion formation in halogenated hydrocarbons.
- Fenzlaff, Marita,Gerhard, Rolf,Illenberger, Eugen
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p. 149 - 155
(2007/10/02)
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- Gas-Phase and Computational Studies of Pentacoordinate Silicon
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We have demonstrated that a wide variety of pentacoordinate silicon anions (siliconates) should be stable and can be prepared by combining the predictive powers of MNDO and ab initio computational methods and the flowing afterglow (FA) experimental technique.MNDO has been used to compute the anion affinities of 91 siliconates; all but five of these are predicted to be stable with respect to the loss of an anion.Twenty-four siliconates, most of them previously unreported, have been prepared and studied in the FA.The MNDO predictions were, in general, consistent with the experimental results and with trends previously reported by Corriu and co-workers, but in some cases they were found deficient.For example, MNDO tends to underestimate the stability of fluorine-containing siliconates.In these cases, we have carried out ab initio computations and found these to be consistent with both the experimental studies reported here and the Corriu trends.
- Damrauer, Robert,Burggraf, Larry W.,Davis, Larry P.,Gordon, Mark S.
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p. 6601 - 6606
(2007/10/02)
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- Uphill Transport of Dihydrogenphosphate Ion through a Liquid Membrane Containing Oxomolybdenum(V) Tetraphenylporphyrin Complex as a Mobile Carrier
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Oxomolybdenum(V) tetraphenylporphyrin complex is useful as a carrier for preparing a polymer-supported liquid membrane system in which H2PO4- ion is transported against its concentration gradient by coupling of a ligand exchange reaction.
- Kokufuta, Etsuo,Nobusawa, Mitsuyuki
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p. 425 - 428
(2007/10/02)
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- Reduction of fluoropentaamminecobalt(III) by 1-ethoxyethyl and 2-hydroxy-2-propyl radicals: A kinetic competition study
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Kinetic competition experiments on the indicated reactions were conducted at 25°C and μ = 1.00 M. The rate constants are as follows: ·C(CH3)2OH, 2.2 × 106 M-1 s-1; ·CH(CH3)OC2H5, 1.1 × 106 M-1 s-1. The independently known rate constants for the competing reagents (Co(en)33+ and Co(NH3)5Cl2+, respectively) were used in the evaluation of the results.
- Mchatton, Ron C.,Espenson, James H.
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p. 784 - 786
(2008/10/08)
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- Gas-Phase Reactions of O- and O2- with a Variety of Halogenated Compounds
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The flowing afterglow technique has been applied to a comparative study, for a series of halogenated compounds, of dissociative attachment and reaction with O- and O2-.The ion product spectrum produced by reaction with O- and O2- overlaps but is more diverse than that obtained by dissociative attachment.Absolute rate constants for the O- and O2- reactions are reported.A few reactions, for which exothermic mechanisms can be written, were found to be quite inefficient.
- Streit, Gerald E.
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p. 2321 - 2324
(2007/10/02)
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- Mobilities of negative halogen ions in various gases
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The mobilities of SF6- in He and of F-, Cl-, Br-, and I- in Ar, Xe, H2, N2, CO, and CH4, have been investigated over the field-strength (E/P) range of 5 to 25 V/cm Torr using time-resolved high pressu
- Fujii, T.,Meisels, G. G.
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p. 5067 - 5069
(2007/10/02)
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- Negative ion-molecule reactions of SF4
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A study of some negative ion-molecule reactions involving SF4 has been carried ot by the flowing afterglow technique at ambient temperature.By ezamining a series of charge exchange reactions of SF4 and SF4-, the electron affinity of SF4 has been determined to be 2.35+/-0.1 eV.Rate coefficients for the charge exchange reactions of HS-, S-, OH-, and O- with SF4 and of SF4- with Cl2 and NO2 are reported.In addition, the fluoride transfer reactions of SF4- and SF6- with SF4 to produce SF5- have been examined.That both reactions proceed indicates that the fluoride affinity of SF4 is greater than that of SF3 or SF5.A lower limit of 3.7 eV for the electron affinity of SF5 may also be deduced from the fluoride transfer reactions.The two body addition of halide ions (X-) to SF4 to form the adduct SF4X- proceeds at near the collision limit (k=9.7*10-10cm3molecule-1s-1) for F-, very slowly (k=2.6*10-11cm3molecule-1s-1) for Cl-1, and not at all within experimental limits (k-12cm3molecule-1s-1) for Br-1.
- Babcock, Lucia M.,Streit, Gerald E.
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p. 3864 - 3870
(2007/10/02)
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- The reaction of fluorosulfuryl isocyanate with alkali metal fluorides
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Fluorosulfuryl isocyanate reacts with cesium, potassium, and sodium fluorides in acetonitrile solvent at 25° to form stable, solid adducts having a molar ratio FSO2NCO: MF close to 1:1. Chemical and physical evidence indicates that these compounds may be formulated as the salts of fluoroformylfluorosulfurylimide, M+[N(SO2F)C(O)F]-.
- Roderiguez, Joseph A.,Noftle, Ronald E.
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p. 1874 - 1877
(2008/10/08)
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- Some perfluoroalkyliminosulfur derivatives
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Trifluoromethyliminosulfur dichloride and pentafluoroethyliminosulfur dichloride are prepared by reaction of aluminum trichloride with trifluoromethyliminosulfur difluoride and pentafluoroethyliminosulfur difluoride, respectively. These imino dichlorides
- Lustig, Max
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p. 1317 - 1319
(2007/10/12)
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- The preparation and properties of N-fluoroformyliminosulfur difluoride, SF2=NCOF
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The inorganic isocyanates derived from silicon, phosphorus, and sulfur have been found to react readily with sulfur tetrafluoride to give, in common, the novel compound, N-fluoroformyliminosulfur difluoride, SF2=NCOF, the preparation and proper
- Clifford, Alan F.,Kobayashi, Calvin S.
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p. 571 - 574
(2007/10/05)
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