Reaction Of CF Research Articles

Formation of Calcium Ferrite Containing Aluminum (CFA) in Sintering of Iron Ore Fines

Calcium ferrite containing aluminum (CFA) is a precursor of the low-temperature bonding phase in the sintering process of iron ore fines for blast furnace ironmaking. Thus, improving the formation of CFA at lower temperature is very important for saving energy, improving efficiency and production. In this paper, the formation process of CFA was investigated at 1200 °C by reactions of alumina (Al2O3), respectively with a mixture of calcium oxide (CaO) and hematite (Fe2O3) and monocalcium ferrite (CF) as a recognized initial product, as well as reaction of Al-containing hematite (Hss) with CF. The result confirmed that CF is an intermediate product formed easily in the sintering process, and it may react with excessive Fe2O3 to generate an alpha-calcium iron oxide (Ca2Fe15.50O25) as a new phase. It was found that CFA can be formed directly by reactions of CF with Hss and Ca2Fe15.50O25 with Al2O3, while the reaction of CF with Al2O3 is more helpful in generating Ca2Fe15.5O25 rather than CFA, simultaneously forming a calcium aluminum oxide (CaAl2O4, CA; CaAl4O7, CA2). It was revealed that the appearance of CA and CA2 is a main reason to hinder CFA formation in the sintering process of iron ore fines.

Synthesis of 2‐Trifluoromethyl‐4‐aminoquinolines via Heating‐Promoted Multi‐component Reaction of CF3‐Imidoyl Sulfoxonium Ylides and Amines with Difluorocarbene as a C1 Synthon†

Comprehensive SummaryA thermally‐induced multi‐component reaction of CF3‐substituted imidoyl sulfoxonium ylides (TFISYs), amines and (triphenylphosphonio)difluoroacetate (PDFA) has been developed, allowing a facile access to 2‐trifluoromethyl‐4‐aminoquinolines in high yields. The reaction proceeds smoothly with or without the addition of sulfur and utilizes difluorocarbene as a C1 synthon under simply heating conditions. Mechanistic study reveals that in‐situ generated thiocarbonyl fluoride, isothiocyanate or gem‐difluoroalkene might act as the key reaction intermediates.

Trifluoromethane Destruction Mechanism in Methane-Oxygen Flame

Based on the known data on the concentrations of intermediate substances and taking into account only those elementary reactions whose kinetic parameters are known, the mechanism of CF3H destruction in a flame of methane-oxygen mixtures of various compositions is developed. It is shown that CF3H destructs in the flame in reactions with O and OH without regeneration. In rich mixture further conversion of CF3H mainly occurs due to the reactions of CF3, CF2, COF2 with atomic hydrogen, which provide inhibition of methane combustion in oxygen by trifluoromethane. In stoichiometric and especially in lean mixture a role of oxidative processes involving O and OH increases and the inhibition effect weakens. The obtained scheme qualitatively describes the entire known experimental pattern observed during the combustion of CH4/O2/CF3H mixtures.

Reversible Li+ Storage in CFx-Based Cathodes through Transition Metal Decomposition

Graphite fluorides (CFx) have been commercially applied in primary lithium batteries for decades with high specific capacity and low self-discharge rate, but the electrode reaction of CF with Li+ is basically irreversible compared to that of transition metal fluorides (MFx, M = Co, Ni, Fe, Cu, etc.). In this work, rechargeable CFx-based cathodes are fabricated by introducing transition metals, which reduces the Rct of the CFx electrode during the primary discharge process and participates in the re-conversion process of LiF under high voltage, which generates MFx (confirmed by ex situ X-ray diffraction measurements) for subsequent Li+ storage. A CF-Cu (F/Cu = 2/1 by mol) electrode, for example, delivers a primary capacity as high as 898 mAh g(CF0.56)-1 (∼2.35 V vs Li/Li+) and a reversible capacity of 383 mAh g(CF0.56)-1 (∼3.35 V vs Li/Li+) in the second cycle. Furthermore, excessive transition metal decomposition during the charge process is harmful to electrode structure stability. Methods such as building a compact counter electrolyte interface (CEI) and obstructing the electron transport of transition metal atoms will contribute to finite and local transition metal oxidation that benefits cathode reversibility.

Silver-Catalyzed Domino Reaction of CF3-Substituted N-Allenamides with Primary Amines for the Construction of 2-Amido-5-fluoropyrroles.

We report herein a domino reaction to construct 2-amido-5-fluoropyrroles from CF3-substituted N-allenamides. The in situ generated gem-difluorinated ene-ynamides derived from CF3-substituted N-allenamides, when subjected to silver catalysis with a primary amine, undergo simultaneous hydroamination of the ynamide moiety followed by a 5-endo-trig addition/β-fluoride elimination sequence, enabling the construction of 2-amido-5-fluoropyrroles. This transformation features excellent functional group compatibility. By employing 2-aminophenols, functionalized benzo-oxazoles were produced.

Elucidation of Discharge Mechanism in CFx As a High Energy Density Cathode Material for Lithium Primary Battery

Fluorinated graphite (CF x ) is a class of cathode materials with the high theoretical capacity (865 mAh g-1 in case of x=1) for primary (non-rechargeable) batteries. When using Li metal as the anode material, the system possesses a very low self-discharge rate (< 0.5% per year at 25 °C) compared to other current alternative chemistries. This system, with the proposed general governing reaction of CF x +Li→LiF+C, is one of the best candidates for a wide range of applications, such as implantable medical devices and equipment for extreme environment.Although the lithium fluorinated graphite system has been under investigation for a few decades, there is still a lack of fundamental understanding of the reaction mechanism in this system. Here, a multiscale investigation on the CFx discharge mechanism was performed using a novel cathode structure to minimize the carbon and fluorine additives for precise cathode characterizations. Titration gas chromatography (TGC), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), cross-sectional focused ion beam (FIB), high-resolution transmission electron microscopy (HRTEM), and scanning transmission electron microscopy with electron energy loss spectroscopy (STEM-EELS) were utilized to investigate this system.The results demonstrated that: (i) There is no lithium deposition or intercalation through the entire discharge. (ii) The CFx structure transforms to a hard-carbon like structure with less sp2 content by increasing depth of discharge. (iii) The crystalline LiF particles uniformly covered the layers of CFx structure with a size range of < 10 nm. A three-step discharge reaction mechanism is proposed in agreement with our electrochemical performances. This work deepens the understanding of CFx as a high energy density cathode material and highlights the need for future investigations on primary battery materials to advance performance. Figure 1

Dynamically Hidden Reaction Paths in the Reaction of CF3 + + CO.

Reaction paths on a potential energy surface are widely used in quantum chemical studies of chemical reactions. The recently developed global reaction route mapping (GRRM) strategy automatically constructs a reaction route map, which provides a complete picture of the reaction. Here, we thoroughly investigate the correspondence between the reaction route map and the actual chemical reaction dynamics for the CF3+ + CO reaction studied by guided ion beam tandem mass spectrometry (GIBMS). In our experiments, FCO+, CF2+, and CF+ product ions were observed, whereas if the collision partner is N2, only CF2+ is observed. Interestingly, for reaction with CO, GRRM-predicted reaction paths leading to the CF+ + F2CO product channel are found at a barrier height of about 2.5 eV, whereas the experimentally obtained threshold for CF+ formation was 7.48 ± 0.15 eV. In other words, the ion was not obviously observed in the GIBMS experiment, unless a much higher collision energy than the requisite energy threshold was provided. On-the-fly molecular dynamics simulations revealed a mechanism that hides these reaction paths, in which a non-statistical energy distribution at the first collisionally reached transition state prevents the reaction from proceeding along some reaction paths. Our results highlight the existence of dynamically hidden reaction paths that may be inaccessible in experiments at specific energies and hence the importance of reaction dynamics in controlling the destinations of chemical reactions.

Asymmetric Defluoroallylation of 4-Trifluoromethylpyridines Enabled by Umpolung C-F Bond Activation.

Carbon-fluorine bond activation of the trifluoromethyl group represents an important approach to fluorine-containing molecules. While selective defluorinative functionalization reactions of CF3 -containing substrates have been achieved by invoking difluorocarbocation, difluorocarboradical, or difluoroorganometallic species as the key intermediates, the transformations via fluorocarbanion mechanism only achieved limited success. Furthermore, the enantioselective defluorinative transformation of the CF3 group remained a formidable challenge. Here we report a defluorinative functionalization reaction of 4-trifluoromethylpyridines involving difluoro(pyrid-4-yl)methyl anion as the key intermediate, which was developed based upon our previous studies on the N-boryl pyridyl anion chemistry. In particular, asymmetric defluoroallylation of 4-trifluoromethylpyridines and -pyrimidines could be achieved by using Ir-catalysis to forge a difluoroalkyl-substituted chiral center.

Antibiotic resistance and drug modification: Synthesis, characterization and bioactivity of newly modified potent ciprofloxacin derivatives

Development of new derivatives of commercial antibiotics using different organic reagents and testing these derivatives against different microorganisms are the main goals of this article. Thus, the antibiotic ciprofloxacin, CF, was acylated via reaction with ethyl cyanoacetate and ethyl acetoacetate in basic medium to give the cyanoacetylpiprazinyl dihydroquinoline derivative 3, and oxobutanoylpiprazinyl dihydroquinoline derivative 5, respectively. On the other hand, N-alkylated derivatives 8–10, were prepared through the reaction of CF with chloroacetonitrile, chloroacetyl acetone and chloroacetone in the presence of carbonate salt. In basic medium, both 3 and 10 were coupled with benzenediazonium chloride to afford hydrazono derivatives, which were then cyclized to give 4-(dihydropyridazinecarbonyl)piperazinyl-1,4-dihydroquinoline. Furthermore, compounds 3 and 10 were reacted with benylidenemalononitrile to produce 4H-pyan and pyrido[1,2-a]pyrazine derivatives, respectively. Both 3 and 10 were reacted with DMFDMA to give enaminone derivatives. These enaminones were cyclized to aminopyrimidine derivatives by reacting with urea or thiourea. X-ray, elemental analysis and spectral data were used to illustrate and confirm the structures of the isolated compounds. The bioactivities of the novel compounds were investigated against different gram-positive and gram-negative bacteria. In addition, these novel antibiotic derivatives were tested against ciprofloxacin-resistant bacteria isolated from patients aged 65–74 years. This study reveals that most of the modified drugs show high to moderate antibacterial activity. Additionally, these drugs show good effects against ciprofloxacin-resistant bacteria.

Mechanistic and kinetics study on the reaction of CF3CBrCH2 with OH: A theoretical study

AbstractQuantum chemical method (CCSD(T)/cc‐pVTZ//M06‐2X/6‐311++G(d,p)) is employed to research the CF3CBrCH2 + OH reaction. The results indicate that the reaction takes place through the interaction of the oxygen atom of the OH radical with the middle C and terminal C atom of CF3CBrCH2 generating adduct IM1 (CF3CBrCH2OH) and IM2 (CF3CBrOHCH2), respectively, and then further dissociation or rearrangement to many products. The rate constants have been computed at 10−10 to 1010 Torr and 200–3000 K by RRKM theory for various product pathways. The results show that at 200–800 K, the rate constant for the production of IM1 (CF3CBrCH2OH) by collisional deactivation is dominant; at high temperatures, the production of P1 (CF3CBrCHOH + H) becomes predominate. The predicted data for CF3CBrCH2 + OH agree closely with available experimental value. The total rate constants are independent on pressure and dependent on temperature. The rate equation can be fitted as k(T) = 1.77 × 10 −7T−0.65exp(−4518.77/T) at 200–300 K, 30 Torr of Ar. The atmospheric lifetime of CF3CBrCH2 in OH is around 2.77 days. TD‐DFT computations imply that IM1, IM2, IM3, IM4, IM5, and IM6 will photolyze under the sunlight.

Direct Enantio- and Diastereoselective Zn-ProPhenol-Catalyzed Mannich Reactions of CF3- and SCF3-Substituted Ketones.

Enantioselective incorporation of trifluoromethyl (-CF3) and trifuoromethylthio (-SCF3) groups in small molecules is of high interest to modulate the potency and pharmacological properties of drug candidates. Herein, we report a Zn-ProPhenol catalyzed diastereo- and enantioselective Mannich addition of α-trifluoromethyl- and α-trifuoromethylthio-substituted ketones. This transformation uses cyclic and acyclic ketones and generates quaternary trifluoromethyl and tetrasubstituted trifuoromethylthio stereogenic centers in excellent yields and selectivities.

Construction of Chiral β-Trifluoromethyl Alcohols Enabled by Catalytic Enantioselective Aldol-Type Reaction of CF3CHN2.

A zinc-/quinine-mediated enantioselective Aldol-type reaction of trifluorodiazoethane (CF3CHN2) with various aldehydes is described. This study demonstrated the feasibility of utilizing CF3CHN2 as an effective hard nucleophile in catalytic asymmetric transformations. Furthermore, the synthetic utility of this protocol is exemplified by the construction of a diverse set of chiral β-trifluoromethylated alcohols, including a valuable HDAC inhibitor precursor.

Preparation and Reactions of CF3‐Containing Phthalides

We have demonstrated that reactions of aromatic 1,2‐diesters and the Ruppert–Prakash reagent (TMSCF3) afforded hitherto unknown phthalides 1 with both trifluoromethyl (CF3) and alkoxy groups at the 3 position, and their unique transformation was also investigated in detail to attain construction of a variety of very rare types of compounds, such as 1,3‐dihydroisobenzofurans 8 as well as indanones 9 with a CF3 moiety, whose behavior was completely different from the structurally similar compound 2a.

Catalytic Asymmetric Mannich Type Reaction with Tri-/Difluoro- or Trichloroacetaldimine Precursors.

A highly efficient catalytic asymmetric Mannich type reaction of CF3-, CF2H-, or CCl3-acetaldimine precursors by a chiral primary amine is presented. This protocol provides facile access to chiral CF3-, CF2H-, or trichloroethyl amines in excellent yields and high enantioselectivity (up to 99% yield, up to >99% ee).

Mild and Regioselective Synthesis of 3‐CF3‐Pyrazoles by the AgOTf‐Catalysed Reaction of CF3‐Ynones with Hydrazines

Gold‐ and silver‐catalysed reactions of trifluoromethylated ynones with aryl (alkyl) hydrazines were investigated. The use of (THD‐Dipp)AuOTf and AgOTf resulted in quick heterocyclization reactions to selectively give 3‐CF3‐pyrazoles. AgOTf was found to be the catalyst of choice, and various 3‐CF3‐pyrazoles were formed in up to 99 % isolated yield with high regioselectivity. The reaction has a broad scope: 3‐CF3‐pyrazoles with alkyl and aryl substituents as well as different functional groups can be prepared by this approach. The known pyrazole drugs Celebrex® and SC‐560 were efficiently prepared to demonstrate the utility of the method. Mechanistic investigations revealed that the reaction involves the formation of a hemiaminal as a key intermediate.

The Unimolecular Reactions of CF3CHF2 Studied by Chemical Activation: Assignment of Rate Constants and Threshold Energies to the 1,2-H Atom Transfer, 1,1-HF and 1,2-HF Elimination Reactions, and the Dependence of Threshold Energies on the Number of F-Atom Substituents in the Fluoroethane Molecules.

The recombination of CF3 and CHF2 radicals in a room-temperature bath gas was used to prepare vibrationally excited CF3CHF2* molecules with 101 kcal mol-1 of vibrational energy. The subsequent 1,2-H atom transfer and 1,1-HF and 1,2-HF elimination reactions were observed as a function of bath gas pressure by following the CHF3, CF3(F)C: and C2F4 product concentrations by gas chromatography using a mass spectrometer as the detector. The singlet CF3(F)C: concentration was measured by trapping the carbene with trans-2-butene. The experimental rate constants are 3.6 × 104, 4.7 × 104, and 1.1 × 104 s-1 for the 1,2-H atom transfer and 1,1-HF and 1,2-HF elimination reactions, respectively. These experimental rate constants were matched to statistical RRKM calculated rate constants to assign threshold energies (E0) of 88 ± 2, 88 ± 2, and 87 ± 2 kcal mol-1 to the three reactions. Pentafluoroethane is the only fluoroethane that has a competitive H atom transfer decomposition reaction, and it is the only example with 1,1-HF elimination being more important than 1,2-HF elimination. The trend of increasing threshold energies for both 1,1-HF and 1,2-HF processes with the number of F atoms in the fluoroethane molecule is summarized and investigated with electronic-structure calculations. Examination of the intrinsic reaction coordinate associated with the 1,1-HF elimination reaction found an adduct between CF3(F)C: and HF in the exit channel with a dissociation energy of ∼5 kcal mol-1. Hydrogen-bonded complexes between HF and the H atom migration transition state of CH3(F)C: and the F atom migration transition state of CF3(F)C: also were found by the calculations. The role that these carbene-HF complexes could play in 1,1-HF elimination reactions is discussed.

Shock Wave and Theoretical Modeling Study of the Dissociation of CH2F2. II. Secondary Reactions.

The thermal dissociation of CH2F2 and the reaction of CF2 with H2 was studied in shock waves over the temperature range 1800-2200 K, monitoring the absorption-time profiles at 248 nm. Besides contributions from CF2, the signals showed strong absorptions from secondary reaction products, probably mostly CH2F formed by the reaction CHF + H2 → CH2F + H. Rate constants of a series of possible secondary reactions were modeled, including falloff curves for the thermal dissociations of CHF, CHF2, and CH2F and rate constants of the reactions CHF + CH2F2 → CHF2 + CH2F, CHF + H2 → CH2F + H, H + CH2F2 → CHF2 + H2, H + CF2 → CF + HF, and H + CF → C + HF. On this basis, concentration-time profiles were simulated and compared with experimental absorption-time profiles.

Kinetic and Spectroscopic Studies of the Reaction of CF2 with H2 in Shock Waves.

The reaction of CF2 with H2 was studied in shock waves by monitoring UV absorption signals. CF2 was prepared by thermal dissociation of C2F4 (or of c-C3F6). The rate constant of the reaction CF2 + H2 → CHF + HF near 2000 K was found to be close to 1011 cm3 mol-1 s-1, consistent with earlier information on the reverse reaction CHF + HF → CF2 + H2 and a modeled equilibrium constant. The kinetic studies were accompanied by spectroscopic investigations. Absorption cross sections of C2F4 between 190 and 220 nm were measured near 1000 K and compared with room-temperature values from the literature. Likewise, absorption cross sections of CF2 near 2000 K were measured between 210 and 300 nm and compared with room-temperature data. Additional superimposed absorption signals were recorded during the reaction and identified by their time dependence and by quantum-chemical calculations employing time-dependent density functional theory. A previously unknown absorption spectrum of CHF radicals near 200 nm was identified and its wavelength dependence determined. Further strong absorptions between 190 and 300 nm were attributed to CH2F and CF radicals. Absorptions at longer wavelengths, reaching up to 510 nm, were postulated to arise from C2 radicals formed at later stages of the reaction.

Theoretical study on the mechanism of reactions of CX3[rad] radicals (X = H, F, Cl and Br) with C20H20 and C20F20 fullerenes

We have applied density functional calculations to study the reactions CX3 + C20H20, and CX3 + C20F20 (X = H, F, Cl and Br) based on two pathways (H- or F-displacement and H- or F-abstraction from C20H20 and C20F20). Our results show that CH3 radical prefers H- or F- abstraction from C20H20 and C20F20 while F-displacement is favorable for the reaction of CF3 with the fullerenes. Exothermic characters of H- or F-abstraction with the lower potential barrier indicate that the H-abstraction will dominate the reaction CCl3 + C20H20 while endothermic characters with high potential barrier heights for two reaction pathways of C20H20 and C20F20 with CBr3 indicate unfavorable thermodynamically and kinetically pathways for these reactions. The exothermic reactions are proceed via reactant-like transition state while endothermic reactions will proceed via “late” and alkyl radical-like transition state, consistent with Hammond's postulate. These results are in line with the distribution of natural charges and electrostatic surface potentials (ESP) of reactants. Among these reactions, the reaction of CF3 with C20F20 is most favorable both thermodynamically and kinetically which indicate that reaction of CF3 with C20F20 and C20H20 is more favorable than CCl3 and CBr3 radicals.

One-Pot Synthesis of Functionalized β-Fluoroalkylated Mannich-Type Products from N-Aryl N,O-Acetals

A variety of functionalized β-amino-β-fluoroalkyl carbonyl compounds are accessible via a novel one-pot Mannich-type reaction of CF 2 - and CF 3 -containing N -aryl N , O -acetals with lithium enolates of ketones, esters, and nitriles. The resulting β-fluoroalkylated β-aminocarbonyl compounds are promising peptide surrogates to be used in drug development and for biological applications.