Journal of Fluorine Chemistry最新文献

The organofluorine chemistry field has steadily increased over the years. In particular, the difunctionalization of unsaturated compounds is an efficient pathway toward the formation of regioselective and highly functionalized aliphatic compounds. This review depicts the recent advances made for simultaneously forming C−FG¹ and C−CF₂FG² on alkenes (FG = functional group) by catalysis. This review highlights approaches involving transition metal-catalyzed transformations and one electron manifold.

Air ingress accident scenarios may result in the oxidation of graphite matrix materials and cause serious safety problems in molten salt reactor. However, the oxidation behavior of the molten-salt-infiltrated graphite remains elusive. In this study, the effect of alkali fluoride salts (LiF, NaF, KF and ternary salt FLiNaK) on the oxidation behavior of graphite powder under air atmosphere was investigated. Thermogravimetric analysis and oxidation tests manifest that the initial oxidation temperature of the graphite is reduced from 720 °C to 510–610 °C, because of the presence of the alkali fluoride salts. The catalytic oxidation effect follows the order of KF > NaF > LiF. Careful characterizations reveal that the pristine graphite is mainly oxidized at the graphite edges, while salt-infiltrated graphite is mainly damaged at the graphitic basal planes. Density functional theory calculations suggest that the doping of alkali metal atoms does not change the physical adsorption feature of the oxygen molecule on the graphite plane surface, but increases its adsorption energy to facilitate the graphite oxidation reactions.

Nafion™ utilizes -SO₃H groups for proton conduction. Using an alternative proton-exchange functionality like -PO₃H₂, -COOH, etc., to replace -SO₃H in ion conductive fluoropolymers has attracted significant attention. For example, composite membranes comprising Nafion™ and perfluoro(carboxylic acid) bearing a -COOH group on its side chains have been used in color-alkali cells to reduce unwanted electrolyte crossovers. In the present paper, we reported a new synthetic strategy for constructing novel -PO₃H₂-bearing fluoropolymers (FBP). Our method employs a ZnI₂-promoted phosphorylation reaction of triethyl phosphite that converts benzyl alcohol on a side chain of a fluoropolymer into a benzylphosphodiester group, followed by trimethylsilyl chloride (TMSCl) hydrolysis to yield FBP. This strategy has enabled us to graft a fluoropolymer side chain directly with phosphonic acid. Although the in-plane proton conductivities of FBP fluoropolymers are lower than those of Nafion™ 115, most FBPs, especially Homo-FBP that has no fluoroalkyl ether group on its side chains, are significantly more stable against hydroxyl radical degradations in Fenton tests. This paper presents a new method for the synthesis of -PO₃H₂-containing fluoropolymers and our work also confirms a novel strategy for enhancing the long-term stability of a proton-conductive fluoropolymer in electrical devices—eliminating or reducing fluoroalkyl ether groups on the side chains of the polymer.

A series of asymmetrically fluorinated 2,2′-bibenzimidazoles were obtained by reaction of benzimidazole-2-carboxylic acid with fluorinated 1,2-phenylenediamines in polyphosphoric acid at elevated temperature. The tautomers of fluorinated 2,2′-bibenzimidazoles with a predominance of isomers containing F atoms in distant position relative to the NH group of the benzimidazole fragment are detected in DMSO‑d6 using NMR spectroscopy. The ratio of tautomers depends on the number and arrangement of F atoms in the initial fluorinated 1,2-phenylenediamines. Under similar conditions fluorinated 1,2-phenylenediamines in the presence of benzimidazole-2-carboxylic acid, but without its participation as well as without it, give fluorinated phenazine-2,3-diamines. The direction of transformation of fluorinated 1,2-phenylenediamines depends on the number and position of F atoms. Under similar conditions phenazine-2,3-diamine is not formed from non-fluorinated 1,2-phenylenediamine, but it is obtained with the presence of fluorinated 1,2-phenylenediamines. When fluorinated 1,2-phenylenediamines contain F atoms simultaneously at the positions 4 and 5, the hydrodefluorination of initial fluorinated 1,2-phenylenediamines occurs, resulting in less fluorinated 2,2′-bibenzimidazoles and phenazine-2,3-diamines. Hydrodefluorination of fluorinated 1,2-phenylenediamines in a polyphosphoric acid at elevated temperatures is the first example of the hydrodefluorination of fluorinated aromatic compounds containing strong donor substituents, such as amino groups. Polyphosphoric acid is shown to be a suitable medium for redox processes.

R1234ye(E) is an environmentally friendly working fluid that can be applied in refrigeration, heat pumps, and organic Rankine cycle systems, but it has issues with oxidative decomposition and flammability. Therefore, based on density functional theory, the oxidative decomposition mechanism of R1234ye(E) has been studied. The results indicate that the oxidative decomposition of R1234ye(E) is a typical chain reaction. The first stage is a chain-initiation reaction, where R1234ye(E) generates a large number of free radicals through initial self thermal decomposition reactions and collision reactions with oxygen. The most likely to occur is path 1–2, which is a homolytic reaction with an energy barrier of only 347.91 kJ/mol. The second stage is the chain-propagation reaction, including the reactions between R1234ye(E) and different free radical and subsequent reactions. The most likely to occur is path 5–1, which is a hydrogen abstraction reaction with an energy barrier of only 21.83 kJ/mol. The last stage is the chain-termination reaction, where the intermediates or products of the above reactions continue to react with the active free radicals until they are consumed. When all the reactants and free radicals are consumed and stable products are generated, the oxidative decomposition reaction ends. The research results provide a reference for the safe application of R1234ye(E) and other HFOs working fluids.

Synthesis of 2,2,3,3-tetraftluoro-γ-aminobutyric acid (tetraF-GABA) starting from commercially available 2,2,3,3-tetrafluorobutane-1,4-diol is described. The straightforward nine-step reaction sequence allowed the production of up to 20 g of the target amino acid in 41 % overall yield. Potentiometric titration revealed increased acidity of both ionizable moieties in the title compound (the pK_a values were diminished by 1.6 and 4.0 units for the COOH and NH₃⁺ groups, respectively, as compared to parent GABA). X-ray diffraction studies and DFT calculations demonstrated different preferential conformations in solid state and solution, although the fluorine gauche effect was observed in both cases.

A metal-free [4 + 1] annulation of ortho-hydroxyphenyl substituted para-quinone methides (p-QMs) and CF₃-imidoyl sulfoxonium ylides (TFISYs) has been described, producing a series of trifluoroacetimidoyl-substituted 2,3-dihydrobenzofuran derivatives in good to excellent yields with good diastereoselectivities under mild conditions.

The site-specific fluorination of organic compounds can alter their electron affinity, EA, which in turn can be used to control their reactivity, physical properties, or binding affinities. Using anion photoelectron spectroscopy, we show that for the multiply fluorinated phenoxy radical, the change in EA is predominantly additive per fluorination and can be predicted by the simple formula: ΔEA = ${\sum }_i$ΔEA_i − ΔEA_C, where the numeric index i indicates the positions of fluorination. A small cooperative effect, ΔEA_C, destabilizes the anion, but this only accounts for 11 % of the total ΔEA, in the extreme case of pentafluorophenolate. Our experimental results are consistent with those calculated using density functional theory, demonstrating the suitability of electronic structure calculations in the prediction of fluorination effects, for practical use in the synthetic design of organofluorines.

Recently, there has been a great strive to find new and efficient methods for the degradation of perfluorinated alkylated substances.

In this research work, we present recent advancements and results in the degradation of the surfactant “cC₆O₄-NH₄⁺” (I) (1,3-dioxo-2-difluoromethylene-4-trifluoromethoxy-5-difluoroammonium acetate dioxole) which demonstrates that it can be efficiently degraded in mild conditions, even at 20 °C.

The results of several different and innovative chemical strategies, such as DMSO induced decomposition at mild temperatures, thermal decomposition, acid/base chemistry induced decomposition, all of which decomposed cC₆O₄ to CO₂ + HF/F⁻ in many cases ≥ 99.9%mol will be presented. All results will be supported by the respective kinetics, rates of reaction, thermodynamic reaction parameters, mechanisms of reaction, decomposition products, qualitative and quantitative spectroscopic analyses.

The reaction conditions for the visible light-induced hydroxy-perfluoroalkylation of olefins were explored using Bayesian optimization (BO). This is the first application of BO to the photoreaction synthesis of fluorinated compounds. Five parameters, including light irradiation intensity, were simultaneously examined, thereby enabling the investigation of the reaction conditions using minimal experimentation. The key parameters were identified by calculating the correlation coefficients for each parameter. Furthermore, individual BO were achieved for different olefins and perfluoroalkyl bromides.