Journal of Fluorine Chemistry最新文献

A halon-free method for the synthesis of gem‑bromofluoroolefins utilizing ethyldibromofluoro-acetate is disclosed via a Wittig type reaction. The reaction system takes advantage of inexpensive and readily available reagents. The method was applied to a wide variety of aryl aldehydes. Both electron donating and electron withdrawing moieties on the aryl ring were tolerated and the desired olefin products were obtained in good to excellent yields.

By reacting CeF₃ with XeF₂ the anhydrous CeF₄ was synthesized and studied by XRD, SEM, FTIR, ¹⁹F NMR spectrometry and thermogravimetry. It was found that CeF₄ undergoes hydration upon keeping in air forming the crystalline hydrate with the approximate formula [CeF₄•0.2H₂O]*0.7H₂O. Water molecules both enter the coordination sphere of cerium and form crystalline hydrates with cerium(IV) fluoride due to OH…F hydrogen bonds in the crystal lattice.

In this work, we present a new method for the facile preparation of aryl-IF₄ compounds using KF and ex situ generated chlorine gas within a two-chamber reactor setup. Notably, the process stands out for its simplicity by omitting the use of specialized equipment and generating less chemical waste than the previously reported works. While demonstrating high efficiency at room temperature, the novel approach provides access to a diverse array of products with moderate to excellent yields.

The synthesis of (trifluoromethyl)alkenes, including fully substituted variants, was achieved from thioketones with in situ-generated (trifluoromethyl)diazoalkanes [CF₃C(R)=N₂] (the Barton–Kellogg reaction). In the presence of sodium methoxide and a catalytic amount of tetrabutylammonium chloride, trifluoromethylated N-tosylhydrazones [CF₃C(R)=NNHTs] derived from trifluoroacetaldehyde hemiacetal (R = H) or trifluoromethyl ketones (R = aryl or alkyl) were employed in the reactions with thioketones. The resulting (trifluoromethyl)diazoalkanes reacted with thioketones, forming (trifluoromethyl)thiirane intermediates. Treatment of these intermediates with trimethyl phosphite readily afforded the substituted (trifluoromethyl)alkenes. Theoretical calculations (DFT, B3LYP/6-31G*) showed that (trifluoromethyl)thiiranes, with less distortion than 2,2-difluorothiiranes, exhibited lower reactivity. Consequently, the involvement of a reducing agent was deemed necessary for the desulfurization step.

The research on SF₆ degradation and conversion is of great significance for environmental protection. Based on the density functional theory, the adsorption process of SF₆ on the TiO₂(001) and TiO₂(101) surfaces was investigated. The results indicate a strong interaction between SF₆ and the TiO₂ surface. Significant structural changes in the SF₆, such as elongation of the S-F bonds, were observed after adsorption, rendering the SF₆ more prone to decomposition. According to Mulliken charge analysis, electron transfer occurs from the TiO₂ surface to the SF₆, revealing SF₆ as an electron acceptor while TiO₂ acts as an electron donor. Analysis of the density of states confirms a pronounced electronic orbital overlap between the S/F atoms of SF₆ and the Ti/O atoms of TiO₂, and the charge density distribution along the Z-axis further supports this charge transfer process. Additionally, experimental studies have demonstrated that TiO₂ photocatalysis can accelerate the degradation of SF₆ during DBD. This study demonstrates the catalytic potential of TiO₂ in the degradation of SF₆ insulating gas and provides theoretical support for the efficient and harmless treatment of SF₆.

The interaction of tris(1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedionato)europium(III), (Eu(FOD)₃), with xenon difluoride in acetonitrile solution was found to be accompanied by chemiluminescence (CL). The kinetic curve of CL at a ratio of reagents Eu³⁺/XeF₂ of 1:2 has a complex form; an initial rapid decrease is replaced by an increase in CL intensity, the maximum of which is reached approximately 10 min after the start of the reaction. Next, an exponential decay of the CL intensity is observed over several tens of minutes. The CL spectrum is located in the wavelength range 400–750 nm and corresponds to the emission of an electronically excited europium (III) ion coordinated with FOD and fluoride ion. Spectral methods were used to identify the reaction products – europium (III) fluoride in the sediment and oxygen difluoride in the gas phase. A mechanism for chemiexcitation of europium(III) has been proposed, including: 1) acceptance of fluorine anion from the XeF₂ molecule by europium ion with the formation of active intermediate XeF⁺; 2) oxidative fluorination of the ligand, which is initiated by the interaction of oxygen atom of the FOD ligand with XeF⁺ cation and ends with the formation of oxygen difluoride and the electronically excited product P*, presumably a fluorinated ketone; 3) non-radiative transfer of excitation energy from P* to the europium ion within its coordination sphere, followed by its radiative deactivation.

The carbon residue is a hazardous waste generated by the aluminum electrolysis production process, which contains a large amount of electrolyte fluoride salts. In order to recover the electrolyte components in carbon residue, this paper proposes a new method of using carbon residue to prepare aluminum fluoride by converting Na₅Al₃F₁₄ and Na₃AlF₆ in carbon residue into aluminum fluoride to realize the recycling of fluoride in carbon residue. In the initial step, optimal parameters for carbon removal during roasting have been determined, including an oxygen flow rate of 7 g/min, a roasting temperature of 670 °C, and a roasting time of 80 min. The roasted clinker is obtained, and the removal rate of carbon reaches 99.95 % while the loss rate of fluorine is 0.48 %. In the second step, the mix anhydrous Al₂(SO₄)₃ with roasted clinker for roasting. The optimal roasting temperature of 670 °C, the time of 10 min, and the mass ratio of anhydrous Al₂(SO₄)₃ to roasted clinker of 5:5 could convert fluoride to AlF₃ products, with a conversion rate of 99.76 % and a loss rate of fluorine of 1.05 %. Finally, by removing sulfate impurities through water leaching for 15 min at 35 °C and with a liquid-solid ratio of 6 ml/g, the loss rate of fluorine is 3.98 %. This process yields AlF₃ with a purity of 94.30 %. The recovery rate of fluorine in the whole process is 94.56 %, which successfully achieves the recycling of fluorine in the carbon residue to obtain AlF₃ products.

NaLuF₄:Yb³⁺,Er³⁺ micrometer prismatic crystals are potential materials for the preparation of optical waveguide devices. However, structural defects and OH^– groups are generated inside and on their surfaces during growth processes. The structural defects and OH^– groups lead to a large depletion of excitation energy and severely quench the downconversion luminescence of Er³⁺. In addition, the Yb³⁺/Er³⁺ co-doping ratio significantly affects the downconversion luminescence of the microcrystals, which in turn affects the performance of the optical waveguide amplifiers based on the microcrystals. By adjusting the co-doping ratio of Yb³⁺ and Er³⁺ in the microcrystals and removing the defects in the crystals, their downconversion luminescence performance was significantly improved. The results showed that the downconversion luminescence under the excitation from a 980 nm laser reached the maximum value when the doping ratio of Yb³⁺ and Er³⁺ was 20:1.5. In addition, the OH^– groups and structural defects in the micrometer crystals were significantly eliminated by ion-exchange and high-temperature annealing treatments, and the crystalline quality was significantly improved. After ion-exchange and high-temperature annealing treatments, the downconversion luminescence enhancement of NaLuF₄:Yb³⁺,Er³⁺ microcrystals was 2.5 times that of the untreated samples.

An interesting product divergence in the reaction of trifluorodiazoethane with arylidene-1,3-indanediones is reported. The reaction conducted using 10 mol% of silver carbonate afforded trifluoromethylspiropyrazolines, while with excess of cesium fluoride in methanol, the cycloaddition was followed by nucleophilic ring opening of the spiropyrazoline to afford trifluoromethylated o-carbomethoxybenzoylpyrazolines. Both protocols work under mild reaction conditions and exhibit good functional group tolerance.