Determination of fluorine in silicate and phosphate rocks,micas and stony meteorites

By making certain modifications to a published procedure for fluorine in rocks, it has been possible to improve stability and extend the range of the method. The modified method has been successfully applied to silicate and phosphate rocks, micas, glass and stony meteorites, containing from 60 p.p.m. to 8% fluorine. Some precautions are recommended for reliable determination of chlorine.     

Fluorine and chlorine behavior in chlorine-rich volcanic rocks from White Island, New Zealand

Extraordinarily high chlorine-bearing volcanic bombs were erupted from White Island volcano on January 25, 1987. The concentrations of fluorine and chlorine were measured in these paralava bombs and their likely parent rocks. The paralavas contain glass with over 1.0 wt.% and up to 1.7% of chlorine. The F/Cl ratios and their relationship with other constituents show that the fluorine and chlorine in the bombs were derived from hydrothermal fluid, most likely concentrated brine in an active Crater Pool.     

Determination of fluorine by proton-induced gamma-ray emission (PIGE) spectrometry in igneous and metamorphic charnockitic rocks from Rogaland (S. W. Norway)

More than 200 specimens from different occurrences of the Rogaland igneous complex and surrounding granulite facies metamorphic rocks (S. W. Norway) have been analysed by a direct non-destructive proton induced gamma-ray emission (PIGE) technique. The fluorine contents vary from <25 ppm to 3500 ppm. There is a good correlation between the concentration of fluorine and that of phosphorus for igneous rocks, suggesting a control of apatite on the F content. In metamorphic rocks, amphibole and biotite besides apatite are the principal cencentrators of fluorine indicating that fluorine in the system is controlled by granulite facies metamorphism conditions.Research Associate of the National Fund for Scientific Research (Belgium)     

Simultaneous determination of fluorine and chlorine in silicate rocks by a rapid spectrophotometric method

A rapid accuiate method is described for simultaneous determination of fluorine and chlorine in silicate rocks by taking, separate aliquots of the single sample dissolution. Fluorine, without separation, was determined by means of the zirconium-criochrome cyanine R complex, whereas chlorine was determined by means of the stable iron (III) thiocyanate complex. The mctliod was tested with standard rocks. Results with geochemical standards were comparable with analyses reported by others. Application to several acidic, mafic, and ultramafic rock samples, gave results with a relative standard deviation of less than 5 %.     

Spin-spin coupling and substituent and halogen isotope shift effects in the fluorine NMR spectra of fluorinated cyclopropanes and cyclopropyl ethers

The (19)F NMR spectra of a series of fluorinated cyclopropanes, most of which contain chlorine or bromine on the ring, have been observed and analyzed. A scheme has been developed to assign the resonances and the molecular stereochemistry, based on substituent effects, comparison of related molecules, and isotope shifts induced by the halogens. Replacement of fluorine by chlorine shifts cis fluorine resonances to lower field, and bromine has an even greater downfield influence. However, the shift effect of bromine compared to chlorine on gem or trans fluorines is variable. The magnitude of the isotope shifts is found to be regularly related to the geometrical relationship of the halogen to the observed fluorine and thus makes a significant contribution to the fluorine assignments. The three-bond spin-spin coupling constants between fluorine atoms in cyclopropanes display unusual behavior and are not helpful for assignment of the fluorine resonances. The signs of the coupling constants have been investigated by spin-tickling experiments, and the previously developed relation of the coupling constant sign to its temperature dependence has been found to be violated for some molecules.     

On the synthesis of chlorine pentafluoride

The reaction between chlorine trifluoride and elemental fluorine was studied in order to find the optimal reaction conditions for the synthesis of chlorine pantafluoride. It has been found that nickel difluoride is a very effective catalyst for the mentioned reaction. The obtained results are expressed as space-time-yield of chlorine pentafluoride.     

Electrophilic and nucleophilic approaches to the synthesis of 3-fluorodiazepam

Electrophilic fluorination of diazepam with elemental fluorine or gas phase acetyl hypofluorite gave 3-fluorodiazepam in 20–60% yields. Nucleophilic displacement of chlorine in 3-chlorodiazepam by fluoride ion also gave 3-fluorodiazepam in modest yields (maximum: 21%). Both of these methods were used for the synthesis of ¹⁸F-labelled 3-fluorodiazepam.     

Catalytic and Noncatalytic Ammonolysis of Chloropentafluorobenzene

Ammonolysis of chloropentafluorobenzene both in the presence and in the absence of copper(I) salt results mainly in replacement of the para- and ortho-fluorine atoms with respect to chlorine rather than replacement of the chlorine atom. Ammonolysis of 4-chloro-2,3,5,6-tetrafluoroaniline and 2-chloro-3,4,5,6-tetrafluoroaniline in the absence of copper(I) salt yields exclusively the corresponding fluorine substitution products, whereas in the presence of copper(I) salt the chlorine atom is replaced. Successive ammonolysis of chloropentafluorobenzene in the presence of copper catalyst along these two paths was put into the basis of a new method for preparation of 2,3,5,6-tetrafluoro-1,4-phenylenediamine.     

Determination of fluorine in organic compounds by epithermal neutron activation analysis

Classical activation analysis of fluorine by thermal neutrons has a limited application because of frequent interference from chlorine, the short half life²⁰F (11.4 s) and too high dead time of detectors. A procedure is described for fluorine determination using¹⁹F (n,p)¹⁹O reaction. Use of a boron carbide shield has no effect on the activity of¹⁹O (boron ratio −1) but considerably reduces background and interference due to¹⁸O (n, γ)¹⁹O reaction. The technique has been successfully applied to the determination of fluorine in organic compounds even in the presence of large amounts of chlorine and oxygen.     

Comparative study of activation analyses for the determination of trace halogens in geological and cosmochemical samples.

Halogens (fluorine, chlorine, bromine and iodine) were determined by activation analyses (neutron activation analysis (NAA), photon activation analysis (PAA) and prompt gamma-ray analysis (PGA)) for geological and cosmochemical solid samples. We studied how each analytical method was for the determination of trace amounts of halogens in rock samples. Radiochemical NAA (RNAA) showed the highest analytical reliability for three halogens (chlorine, bromine and iodine), whereas a set of four halogens (fluorine, chlorine, bromine and iodine) could be determined in principle by radiochemical PAA (RPAA) from a single specimen. Although it is a non-destructive method, PGA showed an analytical sensitivity for chlorine comparable to those of RNAA and RPAA.     

Solvation of halogens in fluorous phases. Experimental and simulation data for F2, Cl2, and Br2 in several fluorinated liquids

The solubility of halogen gases--fluorine, chlorine and bromine--has been determined experimentally in several fluorinated solvents between 283 and 323 K at atmospheric pressure. The solubility of chlorine was studied in perfluorooctane, perfluorohexane, perfluorohexylethane, perfluoromethylcyclohexane, perfluoro-1,3-dimethylcyclohexane, perfluoro-2-butyltetrahydrofuran, and perfluoroperhydrophenanthrene and was found to be on the order of 10(-2) in mole fraction. The solubility of fluorine in the studied fluorinated solvents at 298 K is 1 order of magnitude lower than the solubility of chlorine. The solubility of bromine was studied as a function of temperature in perfluorooctane, and it was found to be higher than that of chlorine but of the same order of magnitude. The experimental studies were complemented by molecular simulation calculations. The molecular force fields used for the halogen gases and for the fluorinated solvents were taken, when possible, from the literature. An intermolecular potential model had to be developed for perfluoro-2-butyltetrahydrofuran, with a functional form of the Lennard-Jones plus point charges type. The solubility of the three gases was calculated by molecular simulation using Widom test-particle insertion. Dissimilar interaction parameters of 0.89 and 0.75 in the Lennard-Jones well depths between the solute and the solvent had to be introduced to reach agreement with the experimental results for chlorine and fluorine solubilities, respectively. The structure of the solutions was studied by analysis of solute-solvent radial distribution functions. It was found that the preferential solvation sites for the halogen gases are the terminal CF3 groups of the different fluorinated solvents.     

Dithiophosphorsäurebetaine

Dithiophosphoric Betaine By substitution of chlorine in pyridinium-chloro-dithiophosphoric betaine (III) by F, Br and N(CH₃)₂ new members of this class of compounds are synthesized. Reaction of the new compounds with alcoholes yields pyridinium-alkoxy-halogenodithiophosphates, among which the fluorine derivatives are especially stable. With HCl and HF pyridinium-chlorofluoro- (XX) and -difluoro-dithiophosphate (XXI) are formed. Substitution of pyridine in pyridinium-fluorodithiophosphoric betaine by trimethylamine yields the corresponding trimethylammonium betaine (XXII). Numerous nmr data of the new compounds are tabulated.     

Adsorption and sequential thermal release of F2, Cl2, and Br2 molecules by a porous organic cage material (CC3-R): Molecular dynamics and grand-canonical Monte Carlo simulations

The adsorption–desorption behavior of fluorine, chlorine, and bromine molecules onto a crystalline porous organic cage, namely CC3-R was calculated at different temperatures using molecular dynamics (MD) and grand-canonical Monte Carlo (GCMC) simulations. Self-diffusion coefficients, radial distribution functions (RDF), and adsorption isotherms were calculated for this purpose. The results show that CC3-R has varied capacities to capture these halogens at ambient and high temperatures, so that the thermal release of fluorine is completed with increasing temperature up to around 70°C and chlorine molecules remain at the CC3-R surface up to 100°C and all bromine molecules are removed from the CC3-R surface at 200°C. We found that bromine self-diffusion was almost independent of temperature between 0 and 100°C in contrast to fluorine and chlorine. Among different diffusion regimes, Knudsen diffusion appears to have an important role in the adsorption of heavy halogens at higher temperatures.     

大同烟煤增压富氧燃烧过程中硫、氯和氟的析出特性

利用高压热重结合傅里叶红外研究了大同烟煤在增压富氧燃烧过程中硫、氯和氟的释放行为,主要考察压力对其析出特性的影响。实验结果表明,压力的改变对煤中硫、氯和氟的迁移转化均有显著影响。随着压力的升高,黄铁矿硫向COS等中间产物的转化率逐渐增加,导致SO2的收率逐步上升,但在3 MPa时,燃煤SO2收率却有所降低。此外,压力升高后反应气氛中CO分压的增加促进了COS的生成,导致其收率逐渐上升。因为煤中有机氯析出和转化与挥发分的释放密切相关,所以高压下挥发分释放量的增加使得煤中有更多的有机氯析出并转化为HCl,而且压力升高后,挥发分燃烧速率和温度的升高促进了无机氟化物分解,HF生成量相应增加。此外,高压下水解反应的强化也提高了HF的收率。     

Certified reference materials for the quality control of fluorine in coal, fly ash and clay

A group of laboratories has worked in various intercomparisons in the frame of the BRC-programme (European Commission) to improve their methods for fluorine determination, especially for coal analysis. These exercises allowed to detect and remove sources of error. Methods were improved to such an extent that the certification of fluorine and chlorine in different materials could be envisaged and the BCR consequently decided to produce coal, fly ash and clay materials certified for their F content. In addition, chlorine was certified in the fly ash CRM.     

Photoisomerization and photocyclization of 4-styrylquinoline derivatives

The photochemical properties of 4-styrylquinoline and its derivatives with fluorine and chlorine atoms and nitro group in the para-position of the styryl moiety were studied. Under irradiation in neutral alcohol solutions, these compounds undergo reversible trans-cis photoisomerization with quantum yields close to 0.5, and the cis-isomers undergo cyclization to give benz[i]phenanthridines with quantum yields that do not exceed 0.01. For several compounds, the primary product of photocyclization, dihydrobenz[i]phenanthridine, was spectrally detected. On passing from the neutral to protonated forms, the photoisomerization quantum yields of these styrylquinolines changed insignificantly, and the photocyclization did not occur at all.     

Zur Dismutierung von C1-Fluorchlorkohlenwasserstoffen an Metalloxid- und Halogenidoberflächen

Dismutation of C₁ – Fluorine Chlorine Hydro Carbons at Surfaces of Metal Oxides and halides Dismutation of C₁-fluorine chlorine hydro carbons has been investigated at surfaces of aluminium and chromium chlorides respectively fluorides. Dismutation reactions have been observed only after halogen exchange at such surfaces of solids which contain both, chloride and fluoride. A mechanism of dismutation is suggested which underlies a concerted chlorine/fluorine and fluorine/chlorine exchange between the solid and the gas phase. The results are discussed in connection with thermodynamically considerations.     

Fluorinated heterocyclic compounds: Selective chlorine/fluorine exchange reactions on pyrimidines

Selective chlorine/fluorine exchange reactions on tetrachloropyrimidine, 6-methyl-, 6-chloromethyl-, 6-dichloromethyl-, and 6-trichloromethyl-2,4,5-trichloropyrimidine are described. Sodium fluoride, potassium fluoride, hydrogen fluoride, and antimony trifluoride were used as the fluorinating agents. It was found that NaF and KF fluorinate only in the heterocyclic nucleus, HF in the nucleus and in the chlorinated methyl group, and SbF₃ only in the chlorinated methyl group. In the first stage of fluorination with NaF only chlorine bound in position 4 of the pyrimidine ring is exchanged. The HF reaction is an equilibrium reaction in which the substitution of the fluorine for the first chlorine atom occurs preferentially in position 2. The behaviour of partly fluorinated pyrimidines in nucleophilic exchange reactions is also discussed.     

Fluorination of Hydrogen-containing with elemental fluorine

The hydrohalo-olefins cis and trans CHC1=CHC1, CHC1=CC1₂, CHC1=CH-CH₂C1 and CH₂=CC1-CH₂C1 have been fluorinated with elemental fluorine to give good yields of hydrohalofluoroalkanes. The best operational conditions for F₂ addition to the double bond rather than hydrogen and/or chlorine atom substitution, dimerization and oligomerization of radical intermediates have been studied. Preliminary studies on the reaction of Freon 12 and Freon 22 towards elemental fluorine have also been carried out.     

Preparation and characterization of simple dihalomethylidene platinum dihalide complexes in reactions of laser-ablated Pt atoms with tetrahalomethanes

Platinum atoms react with tetrachlorofluoromethanes upon laser-ablation and with ultraviolet irradiation to form dihalomethylidene platinum dihalide complexes, CX(2)=PtX(2). These new molecules are identified from carbon-13 and chlorine isotopic shifts, displacements in functional group frequencies as chlorine is replaced with fluorine, and comparison to frequencies calculated by density functional theory. The PtC bond lengths calculated here, 1.810 to 1.816 A, are shorter than analogous bond lengths measured earlier for Pt(II) carbene complexes (1.943-1.950 A). The computed effective Pt-C bond orders range from 1.41 to 1.70 as chlorine is replaced by fluorine since the more electronegative halogen appears to concentrate the Pt 5d orbitals and make them bond better with carbon. These platinum methylidene complexes thus have a substantial amount of double bond character from d(pi)-p(pi) bonding.