共查询到20条相似文献,搜索用时 15 毫秒
1.
选择CH3SO2F电化氟化制备CF3SO2F过程为研究系统,研究了电化氟化过程操作电压和反应时间的关系、操作条件对氟化产物组成的影响规律以及Ni电极在电化氟化过程的变化情况. 实验结果表明,Simons电化学氟化过程主要由三个步骤组成:F-在阳极发生电化学氧化反应生成F,该步骤是Simons电化学氟化过程的控制步骤;在Ni电极上生成的F与Ni或NiF2反应生成高价NiFn (n≥3),NiFn为Simons电化学氟化过程的氟化剂;NiFn可以在电极/电解液界面与有机物发生氟化反应生成氟化产物,也可以发生分解反应生成游离F2,NiFn与有机物发生氟化反应的机理与用CoF3等为氟化剂氟化有机物的机理相同. 但NiFn的反应活性比CoF3高,且在实验条件下极不稳定. 相似文献
2.
Lorraine E. Combettes Dr. Marie Schuler Rakesh Patel Baltasar Bonillo Dr. Barbara Odell Dr. Amber L. Thompson Dr. Tim D. W. Claridge Prof. Véronique Gouverneur 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(41):13126-13132
Various 3‐fluoropyrrolidines and 4‐fluoropyrrolidin‐2‐ones were prepared by 5‐exo‐trig iodocyclisation from allylic fluorides bearing a pending nitrogen nucleophile. These bench‐stable precursors were made accessible upon electrophilic fluorination of the corresponding allylsilanes. The presence of the allylic fluorine substituent induces syn‐stereocontrol upon iodocyclisation with diastereomeric ratios ranging from 10:1 to > 20:1 for all N‐tosyl‐3‐fluoropent‐4‐en‐1‐amines and amides. The sense and level of stereocontrol is strikingly similar to the corresponding iodocyclisation of structurally related allylic fluorides bearing pending oxygen nucleophiles. These results suggest that the syn selectivity observed upon ring closure involves I2–π complexes with the fluorine positioned inside. 相似文献
3.
4.
Ljubomir D. Arsov 《Journal of Solid State Electrochemistry》1998,2(4):266-272
The electrochemical synthesis of polyaniline on a titanium surface in aqueous sulfuric acid solutions with various concentrations
of added aniline has been investigated by cyclic voltammetry. By utilizing a more cathodic potential range (up to −0.6 V)
for the cyclization than is usual (up to −0.2 V) on Pt and Au electrodes, the new voltammetric waves have been deconvoluted
from the already well-known ones for polyaniline.
By simultaneous electrochemical and in situ Raman spectroscopic measurements, the Raman bands of polyaniline electrodeposited
on a Ti electrode, were assigned for potentials of −0.15 V and −0.6 V. It was found that the new monitored waves were closely
related to the so-called “middle” peaks and appear only when the polyaniline reaches an overoxidized state.
Received: 7 August 1997 / Accepted: 4 November 1997 相似文献
5.
Toma? Skapin Gašper Tav?ar Andreja Ben?an Zoran Mazej 《Journal of fluorine chemistry》2009,(12):1086-1092
An overview of the main procedures for the preparation of fluorides with very high surface areas is given. Three processes are outlined: (i) plasma fluorination, (ii) sol–gel route and (iii) oxidative decomposition of inorganic precursors. From all three processes nanostructured metal fluorides with 100–400 m2 g−1 can be obtained. Prevention of the local overheating during fluorination seems to be the key factor to obtain the high surface area fluorides. TEM investigations of AlF3 and CrF3 obtained by oxidative decomposition revealed considerable differences in their morphologies and crystallinity. CrF3 is completely amorphous and unstable under beam. AlF3 contains an amorphous phase and nanocrystalline phases of α-AlF3 and β-AlF3. Nanocrystals are uniformly distributed within the amorphous phase. Also present are the rod-like nanostructures that consist of β-AlF3 and are 5–10 nm wide. 相似文献
6.
Ariyanan Mani Subramanian Tamil Selvan Kanala Lakshminarasimha Phani 《Journal of Solid State Electrochemistry》1998,2(4):242-246
The electrochemical polymerization of benzene via the microemulsion approach yields highly crystalline and anisotropic “spherulitic”
polyparaphenylene (PPP) thin films. The crystalline order and the origin of spherulite morphology are discussed.
Received: 29 July 1997 / Accepted: 27 October 1997 相似文献
7.
《Journal of fluorine chemistry》1998,87(2):157-162
Based on recent developments the nickel fluorides mediated mechanism of Simons process is proposed. It is shown that the yield of perfluorinated products depends on the nature of the starting material and the peculiarities of the adsorptions processes on the surface of the nickel anode. Some useful empirical rules to optimise the process of electrochemical fluorination in anhydrous hydrogen fluoride are formulated. 相似文献
8.
New reprocessing system for spent nuclear reactor fuel using fluoride volatility method 总被引:1,自引:0,他引:1
Our proposed spent nuclear fuel reprocessing technology named FLUOREX, which is a hybrid system using fluoride volatility and solvent extraction, meets the requirements of the future thermal/fast breeder reactors (coexistence) cycle. We have been done semi-engineering and engineering scale experiments on the fluorination of uranium, purification of UF6, pyrohydrolysis of fluorination residues, and dissolution of pyrohydrolysis samples in order to examine technical and engineering feasibilities for implementing FLUOREX. We found that uranium in spent fuels can be selectively volatilized by fluorination in the flame type reactor, and the amount of uranium volatilized is adjusted from 90% to 98% by changing the amount of F2 supplied to the reactor. The volatilized uranium is purified using UO2F2 adsorber for plutonium and purification methods such as condensation and chemical traps for fission products provide a decontamination factor of over 107. Most of the fluorination residues that consist of non-volatile fluorides of uranium, plutonium, and fission products are converted to oxides by pyrohydrolysis at 600-800 °C. Although some fluorides of fission products such as alkaline earth metals and lanthanides are not converted completely and fluorine is discharged into the solution, oxides of U and Pu obtained by pyrohydrolysis are dissolved into nitric acid solution because of the low solubility of lanthanide fluorides. These results support our opinion that FLUOREX has great possibilities for being a part of the future spent nuclear fuel cycle system. 相似文献
9.
Feng Yang Chuanmin Ruan Jinsuo Xu Chenghong Lei Jiaqi Deng 《Fresenius' Journal of Analytical Chemistry》1998,361(2):115-118
A novel H2O2 biosensor was constructed employing α-zirconium phosphate as a new support substrate to hold an electron shuttle toluidine
blue between a glassy carbon electrode and horseradish peroxidase. Toluidine blue was intercalated into α-zirconium phosphate-modified
horseradish peroxidase immobilization matrix cross-linked on a glassy carbon electrode surface via bovine serum albumin-glutaraldehyde.
This co-immobilization matrix of the mediator and the enzyme was formed from the α-zirconium phosphate (α-ZrP)-toluidine blue
(TB) inclusion colloid in which horseradish peroxidase (HRP) was dissolved. Intercalation of TB in layered α-ZrP was investigated
by scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and electrochemical measurements. TB immobilized in
this way underwent a quasi-reversible electrochemical redox reaction at the electrode. Cyclic voltammetry and amperometric
measurements demonstrated good stability and efficiently-shuttled electrons between HRP and the electrode. The sensor responded
rapidly to H2O2 with a detection limit of 3.0 × 10–7 mol/L.
Received: 1 July 1997 / Revised: 13 October 1997 / Accepted: 21 October 1997 相似文献
10.
A new method is described for the determination of ammonium in aqueous solutions with electrodes modified by Prussian blue
(PB). The specific voltammetric response of PB-modified electrodes to ammonium ions is used for their analytical determination.
In the presence of ammonium ions, a concentration-dependent inhibition of the low-spin iron(II/III) system of PB occurs. Only
thallium and rubidium ions cause similar inhibition. A useful electrochemical determination method is thus available for detecting
ammonium ions in the presence of frequently interfering potassium and sodium ions. Paraffin-impregnated graphite electrodes
modified with a mechanically transferred PB layer and bulk-modified PB-composite electrodes are studied. The method is applicable
within a concentration range which extends from 4 × 10−5 mol/l to 10−2 mol/l NH4
+. The composite electrode is used in an electrochemical flow-through system in conjunction with the Kjeldahl method.
Received: 21 April 1997 / Accepted: 28 May 1997 相似文献
11.
Electrochemical formation of barium tungstate (BaWO4) was studied as a model case of electrochemical formation of an advanced oxide material for electronics. BaWO4 is formed on the surface of tungsten electrode during oxidation in alkaline media (pH > 12) containing a corresponding cation.
The analysis of electrochemical as well as electrochemical quartz crystal microbalance (EQCM) data taken during these experiments
identifies at least three qualitatively different steps composing the electrode process. Effects of the potential, applied
current density and alkaline earth metal cation concentration are demonstrated using cyclic voltammetry and galvanostatic
experiments. Specific constraints of the ECC formalism for the electrochemical oxide deposition following from the galvanostatic
data are discussed.
Received: 2 October 1997 / Accepted: 4 December 1997 相似文献
12.
T.M. Rangarajan D. Velayutham M. Noel R.P. Singh 《Journal of fluorine chemistry》2011,132(2):107-7021
The partially fluorinated HF soluble intermediates formed during the electrochemical perfluorination of propionyl chloride (PC) and n-butyryl chloride (n-BC) were analyzed after passing 0%, 25%, 50%, 75% and 100% of theoretical charge required for the fluorination of PC and n-BC. The acid fluorides formed were converted to their corresponding sodium salt by alkali treatment and were separated by methanol extraction. The methanol was subsequently removed from the extract by vacuum distillation and the residue containing partially fluorinated sodium carboxylates was analyzed using 19F and 1H NMR spectra. Initial perfluorination on activated electrode surface indicates the operation of ‘zipper-mechanism’. Formation of partially fluorinated product mixture, initial selectivity towards primary and secondary carbon, carbon chain isomerization and formation of cleaved and coupled products support the general operation of free radical pathway in the overall electrochemical process. 相似文献
13.
Nguyen Quang VuDanielle Grée René GréeEric Brown Gilles Dujardin 《Tetrahedron letters》2003,44(34):6425-6428
Reaction of polysubstituted 2-hydroxyalkyldihydropyrans with DAST led regiospecifically to fluorination at the exocyclic position, except for primary alcohols. Difluorination of carbonylated analogues with deoxo-fluor™ occurred also regioselectively. The unexpected stability and synthetic potential of these new allylic fluorides are discussed. 相似文献
14.
Vyacheslav Vasilevich Slepushkin Boris Mikhailovich Stifatov Sergei Borisovich Stifatov Irina Alexandrovna Tikhonova 《Journal of Solid State Electrochemistry》1999,3(4):234-238
Local electrochemical analysis with a pressed-on electrochemical cell is suggested for the estimation of the quality of coatings
protecting the surface of materials, for the detection of different defects and for the control of the thickness and composition
of coatings. The suggested local electrochemical analysis allows the determination of the throwing power of the electrolytes
used in electrodepositions.
Received: 8 December 1997 / Accepted: 21 August 1998 相似文献
15.
Takashi Okazoe Eisuke Murotani Kunio Watanabe Masahiro Itoh Daisuke Shirakawa Kengo Kawahara Isamu Kaneko Shin Tatematsu 《Journal of fluorine chemistry》2004,125(11):1695-1701
A new synthetic procedure for the preparation of perfluoroalkanesulfonyl fluorides utilizing liquid-phase direct fluorination with elemental fluorine has been developed. Direct fluorination of a partially fluorinated ester, which has alkanesulfonyl fluoride in the end, was synthesized from non-fluorinated counterparts and perfluorinated acid fluoride according to the PERFECT process, gave the desired perfluorinated product in moderate yield as well as by-products arising from CS bond cleavage. The results of the direct fluorination of some model substrates suggest that the CS bond cleavage occurred due to radical formation at the α-position rather than the β-position. 相似文献
16.
Max M. Boudakian 《Journal of heterocyclic chemistry》1968,5(5):683-684
Previous studies on the solvent-free fluorination of partially-chlorinated heterocyclics such as 2-chloropyridine, 2,3,4,6- and 2,3,5,6-tetrachloropyridine, and 2,4,6-trichloropyrimidine with alkali metal fluorides or hifluorides revealed an inconsistent product pattern: degradation, partial or complete halogen exchange could occur. The present study concerned application of the solvent-free halogen exchange technique (potassium fluoride) to 2,6-dichloropyridine (I). The latter, as well as its fluorination products, exhibited good stability at 400° to provide an 80% yield of 2,6-difluoropyridine (III). Moderation of fluorination conditions also permitted isolation of the precursor, 2-chloro-6-fluoropyridine (II), a new compound. The above solvent-free process to III is superior to the previously-reported halogen-exchange route in dimethyl sulfone solvent on the basis of yield, reaction time and number of processing steps. 相似文献
17.
Palladium‐Catalyzed Fluorination of Cyclic Vinyl Triflates: Effect of TESCF3 as an Additive
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Yuxuan Ye Prof. Dr. Takashi Takada Prof. Dr. Stephen L. Buchwald 《Angewandte Chemie (International ed. in English)》2016,55(50):15559-15563
A method for the palladium‐catalyzed fluorination of cyclic vinyl triflates has been developed. As with several previous palladium‐catalyzed fluorination reactions using fluoride salts, controlling the regioselectivity presented a challenge in developing a practical synthetic procedure. The addition of triethyl(trifluoromethyl)silane (TESCF3) was found to effectively address this problem and resulted in drastically improved regioselectivities in this palladium‐catalyzed fluorination reaction. This discovery, along with the use of a new biarylphosphine ligand, allowed for the development of an efficient and highly regioselective protocol for the fluorination of vinyl triflates. This method is compatible with a range of sensitive functional groups and provides access to five‐, six‐, and seven‐membered cyclic vinyl fluorides. 相似文献
18.
W. Zhang M. Dubois K. Guérin F. Masin A. Hamwi C. Varenne P. Thomas J.L. Mansot 《Journal of fluorine chemistry》2010,131(6):676-3573
Several new synthesis methods of fluorinated carbon nanofibres, such as controlled fluorination using fluorinating agent (TbF4 or XeF2), or assisted fluorination under UV and gamma irradiation, are reviewed and compared with the direct fluorination using undiluted fluorine gas. The results highlight the different fluorination mechanisms for the direct fluorination and the new methods. The other advantage of those alternative fluorination routes is the possibility to provide fine tuning of the fluorination level, i.e. from F/C atomic ratio close to zero, as a functionalization, to the unity (CF1) according to the required application, electrochemical or tribological. Two applications are described in this paper as a function of the fluorine content: protection against ozonation and use as solid lubricants. 相似文献
19.
Self-assembled monolayer gold electrode for surfactant analysis 总被引:2,自引:0,他引:2
Marc Gerlache Zühre Senturk Guy Quarin Jean-Michel Kauffmann 《Journal of Solid State Electrochemistry》1997,1(2):155-160
A gold electrode coated with a self-assembled monolayer of octane-thiol (SAM/Au) has been used as an amperometric detector
for the determination of surfactants. This detector operated in the presence of a high percentage of organic solvent and was
adapted to an HPLC System. At the SAM/Au, the electrochemical response of an electroactive tracer (potassium ferricyanide)
was completely inhibited, but, in the presence of a cationic surfactant, the electrochemical reduction was progressively restored.
In flow injection analysis, using the SAM/Au in an amperometric flow-through detector polarised at 0.0 V vs Ag/AgCl, a linear
response (i=f{[surfactant]}) was observed for cationic surfactants e.g. cetylpyridinium chloride in the concentration range 2 × 10−6–1 × 10−3 M. The electrochemical data along with the determination of the ion pair stoichiometry between the redox tracer and the surfactant
suggest an electrochemical response related to ion pair formation and governed by electron transfer by tunneling effect.
Received: 28 January 1997 / Accepted: 7 March 1997 相似文献
20.
Steven Bloom Desta Doro Bume Cody Ross Pitts Prof. Dr. Thomas Lectka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(22):8060-8063
To expand upon the recent pioneering reports of catalyzed sp3 C?H fluorination methods, the next rational step is to focus on directing “radical‐based fluorination” more effectively. One potential solution entails selective C?C bond activation as a prelude to selective fluorination. Herein, we report the tandem photocatalyzed ring‐opening/fluorination reactions of cyclopropanols by 1,2,4,5‐tetracyanobenzene (TCB) and Selectfluor to afford a process tantamount to site‐selective β‐fluorination of carbonyl‐containing compounds. This new approach provides a synthetically mild and operationally simple route to otherwise difficult‐to‐prepare β‐fluorinated products in good yields and with good‐to‐excellent regioselectivity. Remarkably, substrates that contain other usually reactive (e.g., benzylic) sites undergo ring‐opening fluorination preferably. The versatility of this method to give cyclic β‐fluorides from tertiary cyclopropanols and γ‐fluoro alcohols is also highlighted. 相似文献