Species Of Fluoride Research Articles

Reactions of Dichloroacetyl Fluoride in Superacidic Media

AbstractDichloroacetyl fluoride was investigated in the superacids HF/MF5 and DF/MF5 (M=As, Sb). The O‐hemiprotonated species of dichloroacetyl fluoride is formed in the binary superacidic systems HF/MF5 and DF/MF5 (M=As, Sb) as hexafluoridoarsenates and hexafluoridoantimonates. With an excess of the strong Lewis acid SbF5 dichloroacetyl fluoride reacts under the formation of the oxonium salt [CCl2HCF2OX2][SbF6] in the superacidic system XF/SbF5 (X=H, D) after HF‐ or DF‐addition, respectively. The colorless salts were characterized by low‐temperature vibrational spectroscopy, NMR spectroscopy, and single‐crystal X‐ray diffraction. [CCl2HC(OH)F][(CCl2HCOF)2H][SbF6][Sb2F11] and [CCl2HCF2OH2][SbF6] crystallize in the monoclinic space groups P21/c and P21/m, respectively, with two formula units per unit cell each. The crystal structure of the oxonium salt shows strong O(−H)⋅⋅⋅F hydrogen bonds and strong F⋅⋅⋅F interactions. The experimental data are discussed together with quantum chemical calculations at the ωB97XD/aug‐cc‐pVTZ‐level of theory.

Formate paddlewheel of a metal–organic framework with open metal sites as a potential adsorbent and sensor for different species of fluoride (F−, HF, F2H−): a DFT study

Formate paddlewheel of a metal–organic framework with open metal sites as a potential adsorbent and sensor for different species of fluoride (F−, HF, F2H−): a DFT study

Synthesis and Structural Investigation of Protonated Haloacetyl Fluorides

AbstractHerein, we report the O‐monoprotonated species of chloroacetyl fluoride and fluoroacetyl fluoride in the binary superacidic systems HF/MF5 and DF/MF5 (M=As, Sb) as hexafluoridoarsenates and hexafluoridostibates. The colorless salts were characterized by low temperature vibrational spectroscopy, low temperature NMR spectroscopy and single‐crystal X‐ray diffraction. [CClH2C(OH)F][SbF6] crystallizes in the monoclinic space group P21/c with four formula units per unit cell and [CH2FC(OD)F][SbF6] in the triclinic space group P with two formula units per cell. The experimental data are discussed together with quantum chemical calculations at the ωB97XD/aug‐cc‐pVTZ‐level of theory. Protonation leads to significant shortening of the C−F bond due to back‐donation of fluorine lone‐pair electrons.

Highly efficient fluoride removal from water using 2D metal-organic frameworks MIL-53(Al) with rich Al and O adsorptive centers

In this study, metal-organic framework MIL-53(Al) was synthesized and studied to understand the different mechanisms between normal MIL-53(Al) and 2D metal-organic framework MIL-53(Al) for removing fluoride. Comparatively, the 2D MIL-53(Al) had two-dimensional linear morphology rather than block shape, indicating more expose adsorptive sites than normal MIL-53(Al). The batch adsorption experiments were applied to investigate the performance of 2D MIL-53(Al), including pH, adsorption kinetics, and thermodynamics. The 2D MIL-53(Al) (75.50 mg/g) showed better adsorption capacity than normal MIL-53(Al) (35.63 mg/g). The adsorption process of 2D MIL-53(Al) followed the pseudo-first-order model and Langmuir model. The adsorption mechanism of this material was further studied by using experimental characterization and density functional theory calculations in detail. The main adsorptive sites were Al and O in the 2D MIL-53(Al), and the relationship between fluoride binding with Al and O was HF2− > HF > F−. The species of fluoride were HF2−, HF, F at different pH and concentrations. Hence, this study provides a significant way on the application of two-dimensional materials for removing fluoride.

Determination of chemical species of fluoride during uptake mechanism of glass-ionomer cements with NMR spectroscopy

ObjectiveThe aim of the present study was to determine the chemical species formed inside glass-ionomer cements after fluoride uptake and to investigate the depth of penetration of fluoride ions within the cement matrix. MethodsAn experimental fluoride-free glass with composition 2SiO2–AlO3–CaO was produced. The glass powder was mixed with aqueous poly(acrylic acid) (PAA), and allowed to set. The resulting specimens were stored in 20ml KF solution with 1000ppm fluorine for 24h and then placed into the same amount of water as for 24h. A fluoride selective electrode was used to give the F concentration of the respective solutions. 19F MAS-NMR spectra were recorded on powdered cement specimens using a Bruker AVANCE-NEO 600 spectrometer. In addition, SEM observation and EDX chemical analysis were conducted on the cross-section of a carefully fractured specimen. ResultsFluoride was shown to be mainly present in the surface layers of the specimen after placement in the KF solution, and only a small fraction was re-released into water. 19F NMR spectroscopy showed that AlF complexes were formed within the cement. SignificanceThe fluoride taken up by a free-fluoride glass ionomer cement mostly occupies surface layers and is retained because it bonds to aluminum within the matrix. This finding explains why the majority of fluoride taken up by conventional glass ionomer cements is retained.

Adsorption mechanism for removing different species of fluoride by designing of core-shell boehmite

Many kinds of adsorbents have been developed for removing fluoride from water. However, the unclear actual mechanism of fluoride adsorption greatly restricts the structural design and application of novel adsorbents. Based on the understanding of the interaction between hydroxyl and fluoride, a novel core-shell nanostructure of boehmite was synthesized via an in-situ-induced assembly for removing fluoride. The formed polycrystalline boehmite (γ-AlOOH) nanostructure significantly enhances adsorption performance. The transformation of fluoride forms (including F−, HF, HF2−) is closely related to the solution property. The acidic solution is more favorable, mainly because of the conversion of HF (pyrazine) and HF2− (the bifluoride ion) with a strong hydrogen bond effect from fluoride (F−) with pH < 3.18. The lattice plane of (0 0 2) belongs to the dominant face for removing fluoride in this structure. According to the experimental and theoretical calculation, strong bonding of Al, O and H sites with fluoride species (F−, HF, HF2−) in acidic solution are demonstrated, but not in alkaline solution due to OH− interference. The possible mechanism of fluoride adsorption on boehmite (AlOOH) structures is proposed. Our findings show a new potential prospect of structural designing for novel fluoride adsorbent.

Density Functional Theory and Molecular Dynamics insights into the site-dependent adsorption of hydrogen fluoride on kaolinite

The removal of fluoride from water using adsorption on a low-cost mineral such as kaolinite is an important research topic. The present communication uses Density Functional Theory (DFT) and Molecular Dynamics (MD) based simulations to comprehensively investigate the adsorption behaviour of HF, one of the most predominant species of fluoride in the aqueous solutions, on the (0 0 1) surface of kaolinite. The optimum geometric configurations of adsorption of HF on different possible sites on the mineral surface have been established, and the corresponding adsorption energies, bond distances, Partial Density of States (PDOS), Mulliken charges and electron density difference plots have been analyzed to understand the interaction at each site. To explore the site-dependent adsorption behaviour, the interaction of HF has been investigated on different sites such as aluminium centres, surface oxygen atoms (both lying and upright) and cavity site (void space encircled by six aluminium centres). The analysis shows that the F atom has a strong tendency to form hydrogen bonds with the surface H atom on kaolinite. Among the three aforementioned types of adsorption sites considered, the “cavity” site is found to offer the greatest adsorption strength. Further, MD simulations have been undertaken to explain the effect of water on the adsorption and substantiate the bonding mechanism.

Experimental values of the rotational and vibrational constants of deuterated silyl fluoride

ABSTRACTAccurate experimental values of the αA and αB rotation–vibration interaction, and ωi, xij and gij vibrational constants have been extracted from the most recent high-resolution Fourier transform infrared and millimetre-wave measurements in the spectra of the prolate symmetric top SiD3F, between 400 and 2000 cm−1. From the experimental values of the ground state rotational and rovibrational interaction parameters, accurate equilibrium rotational constants have been derived: Ae = 1.432326 (12) cm−1 and Be = 0.4112012 (45) cm−1 for silyl fluoride. The effective ground state structure has also been determined from the observed moments of inertia of SiD3F: r0(Si-D) = 1.4755 (29) Å; r0(Si-F) = 1.5931 (26) Å; θ0(DSiD) = 110.47 (32)° and θ0(DSiF) = 108.45 (56)°. A merge of equilibrium moments of 28SiH3F and 28SiD3F yielded an experimental equilibrium structure of silyl fluoride. This geometry has been found in good agreement with semi-experimental median values, as well as with the recent semi-experimental ab initio equilibrium structure obtained using all data available of the various isotopic species of silyl fluoride.

Modification of tin oxide nanoparticles by fluorocarbon solids via a mechanochemical route

Interfacial reactions at the surface of SnO2 nanoparticles adjacent to the fluorocarbon solids (FCS) under mechanical stressing were compared in an attempt to their modification by introducing fluorine and carbon. Emphasis was laid on the comparison of the reactivity of 3 different species of FCS, i.e., polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), and perfluorooctanoic acid (PFOA). PVdF exhibited the highest reactivity, followed by PTFE and PFOA, as confirmed by Raman, FT-IR, XPS, and 19F MAS NMR spectra. The preferential reactivity could be explained in terms of the electrophilicity of FCS toward the nucleophilic oxygen in SnO2, since the decomposition of FCS is catalyzed by the coexisting SnO2. PFOA behaved in a different manner, due to its carboxylic groups. At the same time, carbon nanospecies were introduced as a decomposed product of FCS. This results in the formation of SnO2:F/C nanocomposite. Fluorine introduced to SnO2 survived even after heating up to 600 °C either in air or in Ar. This indicates the thermal stability of the present partially fluorinated SnO2 nanoparticles.

Rotational spectra of isotopic species of silyl fluoride. Part II: Theoretical and semi-experimental equilibrium structure

The equilibrium structure of silyl fluoride, SiH 3F, has been reinvestigated using both theoretical and experimental data. With respect to the former, quantum-chemical calculations at the coupled-cluster level have been employed together with extrapolation to the basis set limit, consideration of higher excitations in the cluster operator, and inclusion of core correlation as well as relativistic corrections ( r(Si–F) = 1.5911 Å, r(Si–H) = 1.4695 Å, and ∠FSiH = 108.30°). A semi-experimental equilibrium structure has been determined based on the available rotational constants for the various isotopic species of silyl fluoride ( 28SiH 3F, 28SiD 3F, 29SiH 3F, 29SiD 3F, 30SiH 3F, 30SiD 3F, 28SiH 2DF, and 28SiHD 2F) together with computed vibrational corrections to the rotational constants ( r(Si–F) = 1.59048(6) Å, r(Si–H) = 1.46948(9) Å, and ∠FSiH = 108.304(9)°).

Rotational spectra of isotopic species of silyl fluoride. Part I: Lamb-dip measurements and quantum-chemical calculations

The Lamb-dip technique has been employed for recording the rotational spectra of three isotopic species of silyl fluoride, namely 28SiH 3F, 29SiH 3F, and 30SiH 3F, in order to improve the knowledge of their spectroscopic parameters as well as to try to resolve their hyperfine structure. High-level quantum-chemical computations using state-of-the-art coupled-cluster techniques together with core-polarized correlation-consistent basis sets have been employed to provide reliable reference values for the hyperfine parameters involved and have been used to guide the experimental investigation. Analysis of the experimental spectra allowed to improve the accuracy of the known spectroscopic parameters as well as to determine for the first time sextic and octic centrifugal-distortion constants.

Ground state rotational spectrum of nitrogen trifluoride: The K = 3 splittings of 14NF 3 and 15NF 3

The ground state rotational spectrum of the 14NF 3 and 15NF 3 isotopic species of nitrogen fluoride has been observed in the ∼450–810 GHz frequency range. This investigation allowed us to improve the rotational parameters for both isotopologues. In particular, for the first time the K = 3 line splitting parameter and the sextic centrifugal distortion constants have been determined for 15NF 3.

Microwave spectrum of iso-propyl fluoride and structure of iso-propyl halides

The microwave spectra of iso-propyl fluoride and its isotopically substituted species were measured. The rotational constants and the coefficients of the first four terms of the quartic centifugal distortion were determined from the observed frequencies. The r s structure of the molecule was determined from the observed moments of inertia. Stark-effect measurements of several low J transitions were carried out for the normal and (CD 3) 2CHF species. The dipole moment of the normal species of iso-propyl fluoride has components of μ b =1.880±0.007 D and μ c =0.540±0.022 D; the total dipole moment μ total=1.956±0.009 D; it makes an angle of 3°52′ with the CF bond and inclines its positive pole towards the (CH 3) 2C group. The structure and dipole moment of iso-propyl fluoride are compared with those of the other iso-propyl halides and ethyl halides.

ChemInform Abstract: Microwave Spectrum, Structure, and Dipole Moment of Vinyl Fluoride.

Abstract Microwave spectra of vinyl fluoride and its nine isotopic species were measured in order to establish the r s structure. Stark-effect measurements of several low- J transitions were carried out for the normal and three deuterated species. The dipole moment of the normal species of vinyl fluoride is μ a = 1.284 ± 0.004, μ b = 0.712 ± 0.012, and μ total = 1.468 ± 0.007 D and makes an angle of 1°7′ with the CF bond.

Chemical geothermometry in hydrothermal aqueous solutions: the influence of ion complexing

The molal concentrations of free ions and complex species of sodium, potassium, calcium, magnesium, sulfate and fluoride in hydrothermal aqueous solutions have been calculated at various temperatures (in the 150–300°C range) and total chloride molalities, assuming the existence of equilibrium with the mineral paragenesis made up of low-albite, microcline, illite, chlorite, a Ca–Al-silicate, chalcedony, anhydrite, fluorite and calcite. Preliminary results suggest that the computer-calculated compositions match satisfactorily the compositions of real reservoir waters from some known geothermal systems with different chloride contents. The computer-generated compositions have therefore been used to investigate the effect of ion complexing on chemical geothcrmometers. There is little effect of complexing on the Na/K geothermometer, while it is remarkably strong on the K 2/Mg, Ca 1 2 /Na and Ca 1 2 /K geothermometer functions in low chloride environments; the influence of ion association is also important on the SO 4/F 2 geothermometer but at high chloride contents. Where the compatibility of sulfate and fluoride ions is questionable, specific geothermometric functions can he derived taking into account chloride, sulfate and fluoride contents; their use is proposed to get rid of the deviations caused by ion association.

Microwave spectrum, structure, and dipole moment of vinyl fluoride

Microwave spectra of vinyl fluoride and its nine isotopic species were measured in order to establish the r s structure. Stark-effect measurements of several low- J transitions were carried out for the normal and three deuterated species. The dipole moment of the normal species of vinyl fluoride is μ a = 1.284 ± 0.004, μ b = 0.712 ± 0.012, and μ total = 1.468 ± 0.007 D and makes an angle of 1°7′ with the CF bond.

The Harmonic and Anharmonic Force Fields of Nitrosyl Halides

Abstract Harmonic and anharmonic symmetry force constants matrices have been calculated using a stepwise coupling method for the twelve isotopic species of nitrosyl fluoride, chloride and bromide. The valence force fields derived from the above matrices were used to recalculate the normal frequencies and the potential energy distribution among force constants. The valence force fields are compared with others previously reported obtained by different methods.

Submillimeter laser Stark spectroscopy of13CH3F with the 337 ?m line of the HCN laser

Submillimeter laser-Stark spectra have been observed for the isotopic species of methyl fluoride,13CH3F, using the 337 μm line of the HCN laser. We have identified the multiplet transitions as JK=18K←17K in the ground vibrational state. Ten distinct families with K=8, 9, 10, 11, 12, 13, 14, 15, 16 and 17 have been observed. Zero-field frequencies for all the transitions are given and in most cases with better accuracy than predicted from the previous constants.

Structural Species and Activities of Lithium Fluoride and Lithium Hexafluoroaluminate Dissolved in Molten Cryolite.

Structural Species and Activities of Lithium Fluoride and Lithium Hexafluoroaluminate Dissolved in Molten Cryolite.

Structural Species of Calcium Fluoride Dissolved in Cryolite Melts.

Etude des modeles pour la dissolution de CaF 2 dans NaF fondu. Il semble que Ca 2+ ne soit pas l'espece calcique dominante. Formation de CaF 3 − et CaF +