Vanadium fluoride is an inorganic compound of vanadium and fluorine. It is paramagnetic yellow-brown solid, hygroscopic. Unlike the corresponding vanadium tetrachloride, the tetrafluoride is not volatile because it adopts a polymeric structure, it decomposes before melting. VF4 can be prepared by treating VCl4 with HF: VCl4 + 4 HF → VF4 + 4 HClIt was first prepared in this way, it decomposes at 325 °C, undergoing disproportionation to the tri- and pentafluorides: 2 VF4 → VF3 + VF5 The structure of VF4 is related to that of SnF4. Each vanadium centre is octahedral, surrounded by six fluoride ligands. Four of the fluoride centers bridge to adjacent vanadium centres. WebElements Cotton, F. Albert.
Nuclear magnetic resonance spectroscopy
Nuclear magnetic resonance spectroscopy, most known as NMR spectroscopy or magnetic resonance spectroscopy, is a spectroscopic technique to observe local magnetic fields around atomic nuclei. The sample is placed in a magnetic field and the NMR signal is produced by excitation of the nuclei sample with radio waves into nuclear magnetic resonance, detected with sensitive radio receivers; the intramolecular magnetic field around an atom in a molecule changes the resonance frequency, thus giving access to details of the electronic structure of a molecule and its individual functional groups. As the fields are unique or characteristic to individual compounds, in modern organic chemistry practice, NMR spectroscopy is the definitive method to identify monomolecular organic compounds. Biochemists use NMR to identify proteins and other complex molecules. Besides identification, NMR spectroscopy provides detailed information about the structure, reaction state, chemical environment of molecules; the most common types of NMR are proton and carbon-13 NMR spectroscopy, but it is applicable to any kind of sample that contains nuclei possessing spin.
NMR spectra are unique, well-resolved, analytically tractable and highly predictable for small molecules. Different functional groups are distinguishable, identical functional groups with differing neighboring substituents still give distinguishable signals. NMR has replaced traditional wet chemistry tests such as color reagents or typical chromatography for identification. A disadvantage is that a large amount, 2–50 mg, of a purified substance is required, although it may be recovered through a workup. Preferably, the sample should be dissolved in a solvent, because NMR analysis of solids requires a dedicated magic angle spinning machine and may not give well-resolved spectra; the timescale of NMR is long, thus it is not suitable for observing fast phenomena, producing only an averaged spectrum. Although large amounts of impurities do show on an NMR spectrum, better methods exist for detecting impurities, as NMR is inherently not sensitive - though at higher frequencies, sensitivity is higher.
Correlation spectroscopy is a development of ordinary NMR. In two-dimensional NMR, the emission is centered around a single frequency, correlated resonances are observed; this allows identifying the neighboring substituents of the observed functional group, allowing unambiguous identification of the resonances. There are more complex 3D and 4D methods and a variety of methods designed to suppress or amplify particular types of resonances. In nuclear Overhauser effect spectroscopy, the relaxation of the resonances is observed; as NOE depends on the proximity of the nuclei, quantifying the NOE for each nucleus allows for construction of a three-dimensional model of the molecule. NMR spectrometers are expensive. Modern NMR spectrometers have a strong and expensive liquid helium-cooled superconducting magnet, because resolution directly depends on magnetic field strength. Less expensive machines using permanent magnets and lower resolution are available, which still give sufficient performance for certain application such as reaction monitoring and quick checking of samples.
There are benchtop nuclear magnetic resonance spectrometers. NMR can be observed than a millitesla. Low-resolution NMR produces broader peaks which can overlap one another causing issues in resolving complex structures; the use of higher strength magnetic fields result in clear resolution of the peaks and is the standard in industry. The Purcell group at Harvard University and the Bloch group at Stanford University independently developed NMR spectroscopy in the late 1940s and early 1950s. Edward Mills Purcell and Felix Bloch shared the 1952 Nobel Prize in Physics for their discoveries; when placed in a magnetic field, NMR active nuclei absorb electromagnetic radiation at a frequency characteristic of the isotope. The resonant frequency, energy of the radiation absorbed, the intensity of the signal are proportional to the strength of the magnetic field. For example, in a 21 Tesla magnetic field, hydrogen atoms resonate at 900 MHz, it is common to refer to a 21 T magnet as a 900 MHz magnet since hydrogen is the most common nucleus detected, however different nuclei will resonate at different frequencies at this field strength in proportion to their nuclear magnetic moments.
An NMR spectrometer consists of a spinning sample-holder inside a strong magnet, a radio-frequency emitter and a receiver with a probe that goes inside the magnet to surround the sample, optionally gradient coils for diffusion measurements, electronics to control the system. Spinning the sample is necessary to average out diffusional motion, however some experiments call for a stationary sample when solution movement is an important variable. For instance, measurements of diffusion constants are done using a stationary sample with spinning off, flow cells can be used for online analysis of process flows; the vast majority of molecules in a solution are solvent molecules, most regular solvents are hydrocarbons and so contain NMR-active protons. In order to avoid detecting only signals from solvent hydrogen atoms, deuterated solvents are used where 99+% of the protons are replaced with deuterium; the most used deuterated solvent is deuterochloroform, although other solvents may be used depending on the solubility of a sample.
Deuterium oxide and deuterated DMSO (DMSO-d
Calcium fluoride is the inorganic compound of the elements calcium and fluorine with the formula CaF2. It is a white insoluble solid, it occurs as the mineral fluorite, deeply coloured owing to impurities. The compound crystallizes in a cubic motif called the fluorite structure. Ca2 + centres are eight-coordinate; each F− centre is coordinated to four Ca2+ centres. Although packed crystalline samples are colorless, the mineral is deeply colored due to the presence of F-centers; the same crystal structure is found in numerous ionic compounds with formula AB2, such as CeO2, cubic ZrO2, UO2, ThO2, PuO2. A related structure is the antifluorite structure, where the anions and cations are swapped, such as Be2C; the mineral fluorite is abundant, of interest as a precursor to HF. Thus, little motivation exists for the industrial production of CaF2. High purity CaF2 is produced by treating calcium carbonate with hydrofluoric acid: CaCO3 + 2 HF → CaF2 + CO2 + H2O Naturally occurring CaF2 is the principal source of hydrogen fluoride, a commodity chemical used to produce a wide range of materials.
Calcium fluoride in the fluorite state is of significant commercial importance as a fluoride source. Hydrogen fluoride is liberated from the mineral by the action of concentrated sulfuric acid: CaF2 + H2SO4 → CaSO4 + 2 HF Calcium fluoride is used to manufacture optical components such as windows and lenses, used in thermal imaging systems, spectroscopy and excimer lasers, it is transparent over a broad range from ultraviolet to infrared frequencies. Its low refractive index reduces the need for anti-reflection coatings, its insolubility in water is convenient as well. Doped calcium fluoride, like natural fluorite, exhibits thermoluminescence and is used in thermoluminescent dosimeters. CaF2 is classified as "not dangerous", although reacting it with sulfuric acid produces toxic hydrofluoric acid. With regards to inhalation, the NIOSH-recommended concentration of fluorine-containing dusts is 2.5 mg/m3 in air. List of laser types Photolithography Skeletal fluorosis NIST webbook thermochemistry data Charles Townes on the history of lasers National Pollutant Inventory - Fluoride and compounds fact sheet Crystran Material Data MSDS
Manganese fluoride is the inorganic compound with the formula MnF3. This red/purplish solid is useful for converting hydrocarbons into fluorocarbons, i.e. it is a fluorination agent. It forms many derivatives. MnF3 can be prepared by treating a solution of MnF2 in hydrogen fluoride with fluorine: MnF2 + 0.5 F2 → MnF3It can be prepared by the reaction of elemental fluorine with a manganese halide at ~250 °C. Like vanadium fluoride, MnF3 features octahedral metal centers with the same average M-F bond distances. In the Mn compound, however, is distorted due to the Jahn-Teller effect, with pairs of Mn-F distances of 1.79, 1.91, 2.09 Å. The hydrate MnF3.3H2O is obtained by crystallisation of MnF3 from hydrofluoric acid. The hydrate exists with space groups P21/c and P21/a; each consists of the salt +− ). MnF3 forms a variety of derivatives. One example is K2MnF3. MnF3 reacts with sodium fluoride to give the octahedral hexafluoride: 3NaF + MnF3 → Na3MnF6Related reactions salts of the anions MnF52− or MnF4−.
These anions adopt chain and layer structures with bridging fluoride. Manganese remains 6 coordinate and trivalent in all of these materials. Manganese fluoride fluorinates organic compounds including aromatic hydrocarbons and fullerenes. On heating, MnF3 decomposes to manganese fluoride. CoF3, another fluorinating agent based on a transition metal in an oxidising +3 state. Novel syntheses of some binary fluorides: the role of anhydrous hydrogen fluoride Acta Chim. Slov. 1999, 46, pp. 229–238, Zoran Mazej, Karel Lutar and Boris Žemva Knudsen Cell mass spectrometry study of Manganese Trifluoride vaporisation, High temperature corrosion and materials chemistry IV: proceedings of the International Symposium, pp. 521–525, google books National Pollutant Inventory: Fluoride and compounds fact sheet National Pollutant Inventory: Manganese and compounds Fact Sheet
European Chemicals Agency
The European Chemicals Agency is an agency of the European Union which manages the technical and administrative aspects of the implementation of the European Union regulation called Registration, Evaluation and Restriction of Chemicals. ECHA is the driving force among regulatory authorities in implementing the EU's chemicals legislation. ECHA helps companies to comply with the legislation, advances the safe use of chemicals, provides information on chemicals and addresses chemicals of concern, it is located in Finland. The agency headed by Executive Director Bjorn Hansen, started working on 1 June 2007; the REACH Regulation requires companies to provide information on the hazards and safe use of chemical substances that they manufacture or import. Companies register this information with ECHA and it is freely available on their website. So far, thousands of the most hazardous and the most used substances have been registered; the information is technical but gives detail on the impact of each chemical on people and the environment.
This gives European consumers the right to ask retailers whether the goods they buy contain dangerous substances. The Classification and Packaging Regulation introduces a globally harmonised system for classifying and labelling chemicals into the EU; this worldwide system makes it easier for workers and consumers to know the effects of chemicals and how to use products safely because the labels on products are now the same throughout the world. Companies need to notify ECHA of the labelling of their chemicals. So far, ECHA has received over 5 million notifications for more than 100 000 substances; the information is available on their website. Consumers can check chemicals in the products. Biocidal products include, for example, insect disinfectants used in hospitals; the Biocidal Products Regulation ensures that there is enough information about these products so that consumers can use them safely. ECHA is responsible for implementing the regulation; the law on Prior Informed Consent sets guidelines for the import of hazardous chemicals.
Through this mechanism, countries due to receive hazardous chemicals are informed in advance and have the possibility of rejecting their import. Substances that may have serious effects on human health and the environment are identified as Substances of Very High Concern 1; these are substances which cause cancer, mutation or are toxic to reproduction as well as substances which persist in the body or the environment and do not break down. Other substances considered. Companies manufacturing or importing articles containing these substances in a concentration above 0,1% weight of the article, have legal obligations, they are required to inform users about the presence of the substance and therefore how to use it safely. Consumers have the right to ask the retailer whether these substances are present in the products they buy. Once a substance has been identified in the EU as being of high concern, it will be added to a list; this list is available on ECHA's website and shows consumers and industry which chemicals are identified as SVHCs.
Substances placed on the Candidate List can move to another list. This means that, after a given date, companies will not be allowed to place the substance on the market or to use it, unless they have been given prior authorisation to do so by ECHA. One of the main aims of this listing process is to phase out SVHCs where possible. In its 2018 substance evaluation progress report, ECHA said chemical companies failed to provide “important safety information” in nearly three quarters of cases checked that year. "The numbers show a similar picture to previous years" the report said. The agency noted that member states need to develop risk management measures to control unsafe commercial use of chemicals in 71% of the substances checked. Executive Director Bjorn Hansen called non-compliance with REACH a "worry". Industry group CEFIC acknowledged the problem; the European Environmental Bureau called for faster enforcement to minimise chemical exposure. European Chemicals Bureau Official website
Titanium fluoride is a inorganic compound with the formula TiF3. It is a violet solid, it adopts a perovskite-like structure such that each Ti center has octahedral coordination geometry and each fluoride ligand is doubly bridging
Sodium fluoride is an inorganic compound with the formula NaF. It is a colorless or white solid, soluble in water, it is a common source of fluoride in the production of pharmaceuticals and is used to prevent cavities. In 2016 it was the 215 most prescribed medication in the United States with more than 2 million prescriptions. Fluoride salts are added to municipal drinking water for the purposes of maintaining dental health; the fluoride enhances the strength of teeth by the formation of fluorapatite, a occurring component of tooth enamel. Although sodium fluoride is used to fluoridate water and, indeed, is the standard by which other water-fluoridation compounds are gauged, hexafluorosilicic acid and its salt sodium hexafluorosilicate are more used additives in the U. S. Fluoride supplementation has been extensively studied for the treatment of postmenopausal osteoporosis; this supplementation does not appear to be effective. In medical imaging, fluorine-18-labelled sodium fluoride is one of the oldest tracers used in positron emission tomography, having been in use since the 1960s.
Relative to conventional bone scintigraphy carried out with gamma cameras or SPECT systems, PET offers more sensitivity and spatial resolution. Fluorine-18 has a half-life of 110 min; however fluorine-18 is considered to be a superior radiopharmaceutical for skeletal imaging. In particular it has a high and rapid bone uptake accompanied by rapid blood clearance, which results in a high bone-to-background ratio in a short time. Additionally the annihilation photons produced by decay of 18F have a high energy of 511-keV compared to 140-keV photons of 99mTc. Sodium fluoride has a variety of specialty chemical applications in synthesis and extractive metallurgy, it reacts with electrophilic chlorides including acyl chlorides, sulfur chlorides, phosphorus chloride. Like other fluorides, sodium fluoride finds use in desilylation in organic synthesis. Sodium fluoride can be used to produce fluorocarbons via the Finkelstein reaction. Sodium fluoride is used as a cleaning agent. Sodium fluoride is used as a stomach poison for plant-feeding insects.
Inorganic fluorides such as fluorosilicates and sodium fluoride complex magnesium ions as magnesium fluorophosphate. They inhibit enzymes such as enolase. Thus, fluoride poisoning prevents phosphate transfer in oxidative metabolism. Fluorides aqueous solutions of sodium fluoride and quite extensively absorbed by the human body. Fluorides interfere with electron calcium metabolism. Calcium is essential in regulating coagulation. Large ingestion of fluoride salts or hydrofluoric acid may result in fatal arrhythmias due to profound hypocalcemia. Chronic over-absorption can cause hardening of bones, calcification of ligaments, buildup on teeth. Fluoride can cause irritation or corrosion to eyes and nasal membranes; the lethal dose for a 70 kg human is estimated at 5–10 g. Sodium fluoride is classed as toxic by both inhalation and ingestion. In high enough doses, it has been shown to affect the circulatory system. For occupational exposures, the Occupational Safety and Health Administration and the National Institute for Occupational Safety and Health have established occupational exposure limits at 2.5 mg/m3 over an eight-hour time-weighted average.
In the higher doses used to treat osteoporosis, plain sodium fluoride can cause pain in the legs and incomplete stress fractures when the doses are too high. Slow-release and enteric-coated versions of sodium fluoride do not have gastric side effects in any significant way, have milder and less frequent complications in the bones. In the lower doses used for water fluoridation, the only clear adverse effect is dental fluorosis, which can alter the appearance of children's teeth during tooth development. A chronic fluoride ingestion of 1 ppm of fluoride in drinking water can cause mottling of the teeth and an exposure of 1.7 ppm will produce mottling in 30–50 % of patients. As of 2014 there have been only three reported cases of fluoride toxicity associated with the ingestion of fluoride-containing toothpaste; as an example, one of these involved a 45 year old woman who came to her doctor complaining of unusual swelling and pain in her fingers. Tests showed elevated levels of fluoride in her blood.
When questioned about this, the woman admitted to the regular ingestion of large amounts of toothpaste, consuming a tube of it every two days and swallowing 68.5 mg of fluoride every day, because she "liked the taste". When asked to switch to a non-fluoride form of toothpaste, her fluoride levels dropped and her condition subsided. Sodium fluoride is an inorganic ionic compound, dissolving in water to give separated Na+ and F− ions. Like sodium chloride, it crystallizes in a cubic motif where both Na+ and F− occupy octahedral coordination sites.