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1.
An Insight of the Results Provided by Color‐Tuning Studies Made on Ir(III) Complexes: A pi‐Neutral CF3 Group Viewed by Adjusting Energies of pi‐type Molecular Orbitals 下载免费PDF全文
Hung‐Sung Lin Shou‐Yun Lu Fu‐Yung Huang Yan Wu Wei‐Lin Su Shao‐Pin Wang 《中国化学会会志》2015,62(11):939-943
The pi‐nature of a CF3 group can be understood through analysis of its bond orbitals (BOs) mixed into the pi‐type molecular orbitals of CF3‐substituted Ir(ppy)2MDPA+ complexes (ppy=2‐phenyl‐pyridine and MDPA=methylated 2,2′‐dipyridyl amine). It has been found that, through this natural bond orbital analysis, the parent’s molecular orbitals (MOs) can be stabilized by χρ*CF BO via negative hyperconjugation and, simultaneously, destabilized by electron lp(F) BO. Since these two competing pi‐effects are virtually counterbalanced as indicated by the vanishing values of crystal orbital overlap populations, the chemical substitution strategy originated from lowering of HOMO by using this electron‐withdrawing CF3 group has been found effective in color‐tuning to blue region. Based on reduced shielding effect due to de‐ creased χρ‐electron density, the reported position dependent CF3‐substitution effects on pi‐type MOs can also be understood through HOMO/LUMO wavefunction analysis. 相似文献
2.
Dr. Sophie Colombel Dr. Nathalie Van Hijfte Dr. Thomas Poisson Dr. Eric Leclerc Prof. Dr. Xavier Pannecoucke 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(38):12778-12787
A new method for the synthesis of fluorinated α‐C‐glycosides is described. The reactions between highly electrophilic radicals (fluorinated or unfluorinated) and a 2‐benzyloxyglucal or galactal provide 2‐keto‐D ‐arabino‐ or 2‐keto‐D ‐lyxo‐hexopyranosides through an addition/fragmentation process. Sodium borohydride mediated or Meerwein–Ponndorf–Verley (MPV) reduction of these compounds provides α‐C‐glycosides that feature appropriate anchoring groups for further synthetic elaboration. The presence of CF2CO2iPr or CF2Br groups at the pseudo‐anomeric position allows efficient reduction/olefination or Br/Li‐exchange/nucleophilic‐addition sequences. These transformations open the way for the synthesis of fluorinated C‐glycosidic analogues of glycoconjugates. 相似文献
3.
Simone Dedola Sergey A. Nepogodiev David L. Hughes Robert A. Field 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(8):o445-o446
The CuI‐catalysed 1,3‐dipolar cycloaddition of an azide and a terminal alkyne is becoming an increasingly popular tool for synthetic chemists. This is the most representative of the so‐called `click reactions' and it is used to generate 1,4‐disubstituted triazoles in high yield. During studies on such cycloaddition reactions, a reduced reactivity of an α‐glucosyl azide with respect to the corresponding β‐anomer was observed. With the aim of understanding this phenomenon, the structure of the title compound, C14H19N3O9, has been determined at 140 K. The glucopyranosyl ring appears in a regular 4C1 chair conformation with all the substituents in equatorial positions, except for the anomeric azide group, which adopts an axial orientation. The observed bond lengths are consistent with a strong anomeric effect, which is reflected in a change in dipolar character and hence reduced reactivity of the α‐glucosyl azide. 相似文献
4.
Silke Erfle Sebastian Reimann Alina Bunescu Zharylkasyn A. Abilov Anke Spannenberg Peter Langer 《Helvetica chimica acta》2012,95(6):1037-1047
The TiCl4‐mediated [3+3] cyclocondensation of various 1,3‐bis(trimethylsilyloxy)buta‐1,3‐dienes with 1‐chloro‐1,1‐difluoro‐4‐(trimethylsilyloxy)pent‐3‐en‐2‐one provides a regioselective access to novel 6‐(chlorodifluoromethyl)salicylates (=6‐(chlorodifluoromethyl)‐2‐hydroxybenzoates) with very good regioselectivity. For selected products, it was demonstrated that the CF2Cl group can be transformed to CF2H and CF2(Allyl) by free‐radical reactions. 相似文献
5.
Chien‐Huang Tsai 《Surface and interface analysis : SIA》2012,44(5):573-577
Carbon‐like nanofiber (CNF) is synthesized using microwave plasma‐enhanced chemical vapor deposition. We present the effects of fluorocarbon and oxygen (CF4/O2) plasma‐treated on the microstructural, crystal, and field emission (FE) characteristics of CNF by SEM, transmission electron microscopy, micro‐Raman, and FE system. Results showed that the presence of the damaged CNF occurs at 2 min CF4/O2 plasma treatment and some amorphous carbon particles after 10 min CF4/O2 plasma treatment. One can also observe that turn‐on fields were enhanced (2.75 uA/cm2) at 2 min CF4/O2 plasma treatment; this indicates a remarkable FE enhancement of the local emission region in CNFs. Complementary information was obtained by thermal desorption atmospheric pressure ionization mass spectrometry and XPS. It can be found that the broken surface morphologies could be attributed to the chemical reaction exchanged via plasma excitation; a large number of bonding (C–F and C–O) in the CNF was detected. In addition, it is observed that the CNF has higher fluorine desorbed at 277.5 and 427 °C after CF4/O2 plasma treatment. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
6.
Viktor P. Bogdanov Victor A. Brotsman Nikita M. Belov Alexey V. Rybalchenko Vitaliy Yu. Markov Sergey I. Troyanov Alexey A. Goryunkov 《化学:亚洲杂志》2020,15(11):1701-1708
Alkylation of homofullerene [6,6]‐C60(CF2)2? dianion with the set of alkyl halides, RX, was established to demonstrate an effect of RX nature on the conversion, product composition, and regioselectivity. The respective C60(CF2)RH, C60(CF2)R2 and C60(CF2)R’R’’ compounds were obtained in the reaction with sterically unhindered RX, isolated by HPLC and unequivocally characterized. The kinetic studies evidenced SN2 mechanism for both alkylation steps, yielding mono‐ and dialkylated C60(CF2), respectively, and indicated the negative charge localization at the bridgehead carbon atoms as well as a steric hindrance of the CF2 moiety likely to be a key factors for the SN2 reaction mechanism and observed regioselectivity. The significant difference in the rate constants of the first and the second steps is attributed to the different activation barriers predicted by DFT calculations which makes possible to develop synthetic methods for the regioselective preparation of monoalkylated C60(CF2)RH and heterodialkylated C60(CF2)R’R’’ derivatives. 相似文献
7.
Taiki Hayashi Gerald Kehr Klaus Bergander Ryan Gilmour 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(12):3854-3858
Sialic acids are ubiquitous components of mammalian cell membranes and key regulators of cellular recognition events. Located at the non‐reducing termini of bioactive gangliosides, these essential building blocks are fused to the polysaccharide core via a characteristic α‐linkage, and rarely occur in the monomeric form. Effective chemical strategies to enable α‐sialylation are urgently required to construct well‐defined tools for glycomics. To complement existing chemoenzymatic strategies, an α‐selective process has been devised based on the site‐selective introduction of fluorine at C3 (more than 20 examples, up to 90 % yield). Predicated on localized particle charge inversion (C?Hδ+→C?Fδ?), fluorine insertion simultaneously augments the anomeric effect, enhances electrophilicity at C2 and mitigates elimination. A stereochemical induction model is postulated that spans the SN continuum and validates the role of the C?F bond in orchestrating α‐selectivity. 相似文献
8.
Probing the effect of anion structure on the physical properties of cationic 1,2,3‐triazolium‐based poly(ionic liquid)s 下载免费PDF全文
Mona M. Obadia Sébastien Fagour Yakov S. Vygodskii Frédéric Vidal Anatoli Serghei Alexander S. Shaplov Eric Drockenmuller 《Journal of polymer science. Part A, Polymer chemistry》2016,54(14):2191-2199
To extensively explore the influence of anion structure on the physical properties of poly(ionic liquid)s (PILs) a series of PILs having main‐chain 1,2,3‐triazolium cations was synthesized via copper(I)‐catalyzed azide‐alkyne 1,3‐dipolar cycloaddition (CuAAC) followed by N‐alkylation with iodomethane and anion metathesis with different metal salts, that is, Li(CF3SO2)2N, Li(CF3CF2SO2)2N, K(FSO2)2N, K(CF3SO2)N(CN), Ag(CN)2N, and sodium 4,5‐dicyano‐1,2,3‐triazolate. To isolate the effect of anion on physical properties of PILs, a common iodide precursor was used to maintain constant the average degree of polymerization (DPn) and chain dispersity. Detailed structure/properties relationship analyses demonstrated a lack of correlation between anion chemical structure, ionic conductivity, and glass transition temperatures. Among synthesized series, the PIL derivative having bis(trifluoromethylsulfonyl)imide counter anion showed the best compromise in performance: low glass transition temperature (Tg = ?68 °C), high thermal stability (Tonset = 340 °C) and superior ionic conductivity (σDC = 8.5 × 10? 6 S/cm at 30 °C), which makes it an interesting candidate for various key modern electrochemical applications. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2191–2199 相似文献
9.
Palladium‐Catalyzed Cascade CH Trifluoroethylation of Aryl Iodides and Heck Reaction: Efficient Synthesis of ortho‐Trifluoroethylstyrenes 下载免费PDF全文
Hao Zhang Dr. Pinhong Chen Prof. Dr. Guosheng Liu 《Angewandte Chemie (International ed. in English)》2014,53(38):10174-10178
A palladium‐catalyzed selective C? H bond trifluoroethylation of aryl iodides has been explored. The reaction allows for the efficient synthesis of a variety of ortho‐trifluoroethyl‐substituted styrenes. Preliminary mechanistic studies indicate that the reaction might involve a key PdIV intermediate, which is generated through the rate‐determining oxidative addition of CF3CH2I to a palladacycle; the bulky nature of CF3CH2I influences the reactivity. Reductive elimination from the PdIV complex then leads to the formation of the aryl–CH2CF3 bond. 相似文献
10.
Shizheng Zhu Guoling Xu Chaoyue Qin Xu Yong Chu Qianli Darryl D. DesMarteau 《Heteroatom Chemistry》1999,10(2):147-151
Halogenation of the potassium or silver salts of bis((trifluoromethyl)sulfonyl)methane(CF3SO2)2CH2 and its cyclo analogues (CF2)nSO2‐CH2SO2CF2 with N‐fluoro‐bis((trifluoromethyl)sul‐fonyl)imine (CF3SO2)2NF, chlorine or bromine gave good yields of the corresponding α‐halo disulfones (CF3SO2)2CHX and (CF2)nSO2CHXSO2CF2 (X: F, Cl, Br; n = 1,2). Some chemical transformations of these fluorinated α‐halo‐disulfones are described. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 147–151, 1999 相似文献
11.
Shuo Huang Fang Wan Songshan Bi Jiacai Zhu Zhiqiang Niu Jun Chen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(13):4357-4361
The self‐healing of zinc‐ion batteries (ZIBs) will not only significantly improve the durability and extend the lifetime of devices, but also decrease electronic waste and economic cost. A poly(vinyl alcohol)/zinc trifluoromethanesulfonate (PVA/Zn(CF3SO3)2) hydrogel electrolyte was fabricated by a facile freeze/thaw strategy. PVA/Zn(CF3SO3)2 hydrogels possess excellent ionic conductivity and stable electrochemical performance. Such hydrogel electrolytes can autonomously self‐heal by hydrogen bonding without any external stimulus. All‐in‐one integrated ZIBs can be assembled by incorporating the cathode, separator, and anode into hydrogel matrix since the fabrication of PVA/Zn(CF3SO3)2 hydrogel is a process of converting the liquid to quasi‐solid state. The ZIBs show an outstanding self‐healing and can recover electrochemical performance completely even after several cutting/healing cycles. 相似文献
12.
Norman Lu Wen‐Han Tu Zong‐Wei Wu Yuh‐Sheng Wen Ling‐Kang Liu 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(6):o289-o291
As part of a homologous series of novel polyfluorinated bipyridyl (bpy) ligands, the title compound, C16H14F6N2O2, contains the smallest fluorinated group, viz. CF3. The molecule resides on a crystallographic inversion centre at the mid‐point of the pyridine Cipso—Cipso bond. Therefore, the bpy skeleton lies in an anti conformation to avoid repulsion between the two pyridyl N atoms. Weak intramolecular C—H...N and C—H...O interactions are observed, similar to those in related polyfluorinated bpy–metal complexes. A π–π interaction is observed between the bpy rings of adjacent molecules and this is probably a primary driving force in crystallization. Weak intermolecular C—H...N hydrogen bonding is present between one of the CF3CH2– methylene H atoms and a pyridyl N atom related by translation along the [010] direction, in addition to weak benzyl‐type C—H...F interactions to atoms of the terminal CF3 group. It is of note that the O—CH2CF3 bond is almost perpendicular to the bpy plane. 相似文献
13.
Internal Dynamics in Halogen‐Bonded Adducts: A Rotational Study of Chlorotrifluoromethane–Formaldehyde 下载免费PDF全文
Dr. Qian Gou Dr. Gang Feng Dr. Luca Evangelisti Dr. Montserrat Vallejo‐López Lorenzo Spada Prof. Dr. Alberto Lesarri Dr. Emilio J. Cocinero Prof. Dr. Walther Caminati 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(10):4148-4152
The rotational spectra of two isotopologues of the 1:1 complex between chlorotrifluoromethane and formaldehyde have been recorded and analyzed by using Fourier‐transform microwave spectroscopy. Only one rotamer was detected, with the two constituent molecules held together through a Cl???O halogen bond (RCl???O=3.048 Å). The dimer displays two simultaneous large‐amplitude intramolecular motions. The internal rotation of formaldehyde around its symmetry axis (V2=28(5) cm?1) splits all the rotational transitions into two component lines with a relative intensity ratio of 1:3. On the other hand, the almost free internal rotation (V3≈2.5 cm?1) of the CF3 symmetric top increases the “rigid” value of the rotational constant A by almost one order of magnitude. In addition, all the transitions display a hyperfine structure due to the 35Cl (or 37Cl) nucleus quadrupole effects. 相似文献
14.
Andrea Mazzanti Dr. Lodovico Lunazzi Prof. Renzo Ruzziconi Prof. Sara Spizzichino Manfred Schlosser Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(30):9186-9192
By making use of a novel diastereotopicity probe, namely C(CF3)2OH, it has been possible to measure by very low temperature 19F NMR spectroscopy the elusive aryl–aryl rotation barriers of biphenyls bearing an OH or F group in one ortho position. The experimental values (5.4 and 4.4 kcal mol?1, respectively) are matched by those from ab initio calculations (5.3 and 4.3 kcal mol?1, respectively). 相似文献
15.
Asymmetric anionic polymerizations of 7‐(o‐substituted phenyl)‐2,6‐dimethyl‐1,4‐benzoquinone methides: Electrostatic interaction and steric,inductive, and resonance effects of the ortho‐substituent on the optical activity 下载免费PDF全文
Takahiro Uno Shuhei Yamamoto Atsushi Yamane Masataka Kubo Takahito Itoh 《Journal of polymer science. Part A, Polymer chemistry》2017,55(6):1048-1058
7‐(o‐Substituted phenyl)‐2,6‐dimethyl‐1,4‐benzoquinone methides which have an electron‐donating methoxy‐(o‐OMe, 2a ) and methyl‐ (o‐Me, 2b ) substituents or an electron‐withdrawing cyano‐ (o‐CN, 2c ) and trifluoromethyl‐ (o‐CF3, 2d ) substituents at the ortho‐position of the aromatic ring and 7‐(m‐substituted phenyl)‐2,6‐dimethyl‐1,4‐benzoquinone methide with an electron‐withdrawing trifluoromethyl‐ (m‐CF3, 2e ) substituent at the meta‐position of the aromatic ring were synthesized, and their asymmetric anionic polymerizations using the complex of lithium 4‐isopropylphenoxide with (?)‐sparteine were carried out in toluene at 0 °C. The polymers with negative optical activity were obtained for all of five monomers, and their specific rotation values largely changed depending upon the substituents of the monomers. On the basis of the comparison of various substituents effects, it was found that the specific rotation of obtained polymers is significantly affected by the electronic effects such as inductive and resonance effects rather than the steric and electrostatic effects of the substituent. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 1048–1058 相似文献
16.
Qiu‐Cheng Chen Matan Soll Dr. Amir Mizrahi Dr. Irena Saltsman Dr. Natalia Fridman Prof. Magal Saphier Prof. Zeev Gross 《Angewandte Chemie (International ed. in English)》2018,57(4):1006-1010
Corrole and sapphyrin with the smallest meso‐substituents reported so far were prepared in a one‐pot synthesis that relies on a non‐aldehydic precursor for introducing CF3 groups. The substantial amounts of products obtained by this facile pathway allowed for the full characterization of 5,10,15‐tris(trifluoromethyl)corrole, the access to a variety of stable chelates thereof and investigations that disclose the unique structural and chemical properties induced by the CF3 substituents. The novel 5,10,15,20‐tetra(trifluoromethyl)sapphyrin undergoes only single protonation, which according to its crystal structure is stabilized by favorable non‐bonding F/H interaction between the meso‐CF3 and the inverted pyrrolic NH. 相似文献
17.
Kazuaki Yokota Toyoji Kakuchi Toshifumi Satoh Stoshi Umeda Masatoshi Kamada 《Macromolecular Symposia》2000,157(1):13-20
The selective cyclopolymerization of 1,2:5,6‐dianhydrohexitols corresponding to diepoxides was a new synthetic strategy for polycarbohydrates, though the polymer is a lack of the anomeric linkage which is found in the naturally occurring polysaccharides. 1,2:5,6‐Dianhydro‐3,4‐di‐O‐methyl‐D‐mannitol, L‐iditol, and D‐glucitol were polymerized using t‐BuOK and BF3·Oet2 to produce the polymers consisting of five‐membered rings. On the other hand, the polymers consisting of six‐membered rings were obtained by the cationic and anionic polymerizations of meso allitol and galactitol monomers, respectively. 相似文献
18.
Thomas Albers Joseph Grobe Duc Le Van Andreas H. Maulitz Ernst‐Ulrich Würthwein 《Heteroatom Chemistry》2005,16(5):406-419
The extremely labile perfluoro‐2‐arsapropene F3CAsCF2 ( 1 ) has been generated by an improved pyrolysis process of Me3SnAs(CF3)2 and found to be stabilized by the presence of hexamethyldisiloxane and tert‐butylphosphaethyne, thus allowing (i) reactivity studies with alkyne derivatives like tBuCP, (iPr)2NCP, MeCCN(iPr)2, HCCOEt and (ii) a full NMR investigation of 1 (19F, 13C). Due to the instability of 1 and some of the products, the [2+2]‐cycloaddition reactions gave the expected arsaphospha‐ and arsa‐cyclobutene derivatives, respectively, in moderate to good yields, but in some cases contaminated with side and/or decomposition products. Unequivocal characterization of the novel compounds was accomplished by spectroscopic in‐ vestigations (1H, 13C, 19F, 31P NMR, IR, MS) supported by comparison with the data of the more stable phosphorus analogues. An interesting isomerization was observed for the 2‐dialkylamino‐4,4‐difluoro‐ 1‐trifluoromethyl‐1‐arsa‐3‐phospha‐2‐cyclobutenes yielding the more stable 3‐dialkylamino‐2,4‐difluoro‐ 1‐trifluoromethyl‐1‐arsa‐2‐phospha‐3‐cyclobutenes. Quantum chemical calculations [B3LYP/6‐311+ G(d,p)] of HAsCH2, F3CAsCF2, and F3CPCF2 were carried out to compare the length of the AsC double bond with the literature data and to elucidate substituent effects on its electronic structure. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:406–419, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20118 相似文献
19.
Donald R. Burgess Jr. Valeri I. Babushok Gregory T. Linteris Jeffrey A. Manion 《国际化学动力学杂志》2015,47(9):533-563
In this work, we report a detailed chemical kinetic mechanism to describe the flame inhibition chemistry of the fire‐suppressant 2‐bromo‐3,3,3‐trifluoropropene (2‐BTP), under consideration as a replacement for CF3Br. Under some conditions, the effectiveness of 2‐BTP is similar to that of CF3Br; however, like other potential halon replacements, it failed an U.S. Federal Aviation Authority (FAA) qualifying test for its use in cargo bays. Large overpressures are observed in that test and indicate an exothermic reaction of the agent under those conditions. The kinetic model reported herein lays the groundwork to understand the seemingly conflicting behavior on a fundamental basis. The present mechanism and parameters are based on an extensive literature review supplemented with new quantum chemical calculations. The first part of the present article documents the information considered and provides traceability with respect to the reaction set, species thermochemistry, and kinetic parameters. In additional work, presented more fully elsewhere, we have combined the 2‐BTP chemical kinetic mechanism developed here with several other submodels from the literature and then used the combined mechanism to simulate premixed flames over a range of fuel/air stoichiometries and agent loadings. Overall, the modeling results qualitatively predicted observations found in cup‐burner tests and FAA Aerosol Can Tests, including the extinguishing concentrations required and the lean‐to‐rich dependence of mixtures. With these data in hand, in a second phase of the present work, we perform a reaction path analysis of major species under several modeled conditions. This analysis leads to a qualitative understanding of the ability of 2‐BTP to act as both an inhibitor and a fuel, depending on the conditions and suggests areas of the kinetic model that should be further investigated and refined. 相似文献
20.
The reaction of alkynyldifluoroboranes RC≡CBF2 (R = (CH3)3C, CF3, (CF3)2CF) with organyliodine difluoride R′IF2 bearing electron‐withdrawing polyfluoroorganyl groups R′ = C6F5, (CF3)2CFCF=CF, C4F9, and CF3CH2 leads to the corresponding alkynyl(organyl)iodonium salts [(RC≡C)(R′)I][BF4]. This approach uses a widely applicable method as demonstrated for a representative series of polyfluorinated aryl‐, alkenyl‐, and alkyliodine difluorides. Generally, these syntheses proceed with good yields and deliver pure iodonium salts. The distinct electrophilic nature of their [(RC≡C)(R′)I]+ cations is deduced from multinuclear magnetic resonance data. Within the series of new iodonium salts [CF3C≡C(C4F9)I][BF4] is an intrinsic unstable one and decomposed forming CF3C≡CI and C4F10. 相似文献