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Fluorine-19 NMR
Fluorine-19 nuclear magnetic resonance spectroscopy (fluorine NMR or 19F NMR) is an analytical technique used to detect and identify fluorine-containing compounds. 19F is an important nucleus for NMR spectroscopy because of its receptivity and large chemical shift dispersion, which is greater than that for proton nuclear magnetic resonance spectroscopy. Operational details 19F has a nuclear spin (I) of and a high gyromagnetic ratio. Consequently, this isotope is highly responsive to NMR measurements. Furthermore, 19F comprises 100% of naturally occurring fluorine. The only other highly sensitive spin NMR-active nuclei that are monoisotopic (or nearly so) are 1H and 31P. Indeed, the 19F nucleus is the third most receptive NMR nucleus, after the 3H nucleus and 1H nucleus. The 19F NMR chemical shifts span a range of about 800 ppm. For ''organo''fluorine compounds the range is narrower, being about −50 to −70 ppm (for CF3 groups) to −200 to −220 ppm ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CFCl3
Trichlorofluoromethane, also called freon-11, CFC-11, or R-11, is a chlorofluorocarbon (CFC). It is a colorless, faintly ethereal, and sweetish-smelling liquid that boils around room temperature. CFC-11 is a Class 1 ozone Ozone () (or trioxygen) is an Inorganic compound, inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , break ...-depleting substance which damages Earth's protective ozone layer, stratospheric ozone layer. R-11 is not flammable at ambient temperature and pressure but it can become very combustible if heated and ignited by a strong ignition source. Historical use Trichlorofluoromethane was first widely used as a refrigerant. Because of its high boiling point compared to most refrigerants, it can be used in systems with a low operating pressure, making the mechanical design of such systems less demanding than that of hig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Contrast Agent
A contrast agent (or contrast medium) is a substance used to increase the contrast of structures or fluids within the body in medical imaging. Contrast agents absorb or alter external electromagnetism or ultrasound, which is different from radiopharmaceuticals, which emit radiation themselves. In X-ray imaging, contrast agents enhance the radiodensity in a target tissue or structure. In magnetic resonance imaging (MRI), contrast agents shorten (or in some instances increase) the relaxation times of nuclei within body tissues in order to alter the contrast in the image. Contrast agents are commonly used to improve the visibility of blood vessels and the gastrointestinal tract. The types of contrast agent are classified according to their intended imaging modalities. Radiocontrast media For radiography, which is based on X-rays, iodine and barium are the most common types of contrast agent. Various sorts of iodinated contrast agents exist, with variations occurring between the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nanoparticle
A nanoparticle or ultrafine particle is a particle of matter 1 to 100 nanometres (nm) in diameter. The term is sometimes used for larger particles, up to 500 nm, or fibers and tubes that are less than 100 nm in only two directions. At the lowest range, metal particles smaller than 1 nm are usually called atom clusters instead. Nanoparticles are distinguished from microparticles (1-1000 μm), "fine particles" (sized between 100 and 2500 nm), and "coarse particles" (ranging from 2500 to 10,000 nm), because their smaller size drives very different physical or chemical properties, like colloidal properties and ultrafast optical effects or electric properties. Being more subject to the Brownian motion, they usually do not sediment, like colloid, colloidal particles that conversely are usually understood to range from 1 to 1000 nm. Being much smaller than the wavelengths of visible light (400-700 nm), nanoparticles cannot be seen with ordinary ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to generate pictures of the anatomy and the physiological processes inside the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves to form images of the organs in the body. MRI does not involve X-rays or the use of ionizing radiation, which distinguishes it from computed tomography (CT) and positron emission tomography (PET) scans. MRI is a medical application of nuclear magnetic resonance (NMR) which can also be used for imaging in other NMR applications, such as NMR spectroscopy. MRI is widely used in hospitals and clinics for medical diagnosis, staging and follow-up of disease. Compared to CT, MRI provides better contrast in images of soft tissues, e.g. in the brain or abdomen. However, it may be perceived as less comfortable by patients, due to the usually longer and louder measurements with the subject in a long, confining tube, although ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acetone-d6
Deuterated acetone ((CD)CO), also known as acetone-d, is a form (isotopologue) of acetone (CH)CO in which the hydrogen atom (H) is replaced with deuterium (heavy hydrogen) isotope (H or D). Deuterated acetone is a common solvent used in NMR spectroscopy. Properties As with all deuterated compounds, the properties of deuterated acetone are virtually identical to those of regular acetone. Manufacture Deuterated acetone is prepared by the reaction of acetone with heavy water, HO or DO, in the presence of a base. In this case, the base used is deuterated lithium hydroxide Lithium hydroxide is an inorganic compound with the formula LiOH. It can exist as anhydrous or hydrated, and both forms are white hygroscopic solids. They are soluble in water and slightly soluble in ethanol. Both are available commercially. While ...: In order to fully deuterate the acetone, the process is repeated several times, distilling off the acetone from the heavy water, and re-running the reaction in a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
C6D6
Deuterated benzene (C6D6) is an isotopologue of benzene (C6H6) in which the hydrogen atom ("H") is replaced with deuterium (heavy hydrogen) isotope ("D"). Properties The properties of deuterated benzene are very similar to those of normal benzene, however, the increased atomic weight of deuterium relative to protium means that the melting point of C6D6 is about 1.3 °C higher than that of the nondeuterated analogue. The boiling points of both compounds, however, are the same: 80 °C. Applications Deuterated benzene is a common solvent used in NMR spectroscopy. It is widely used for taking spectra of organometallic compounds, which often react with the cheaper deuterated chloroform. A slightly more exotic application of C6D6 is in the synthesis of molecules containing a deuterated phenyl group. Deuterated benzene will undergo all the same reactions its normal analogue will, just a little more slowly due to the kinetic isotope effect. For example, deuterated benzene coul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CDCl3
Deuterated chloroform, also known as chloroform-''d'', is the organic compound with the formula . Deuterated chloroform is a common solvent used in NMR spectroscopy. The properties of (chloroform) are virtually identical. Deuterochloroform was first made in 1935 during the years of research on deuterium. Preparation Deuterated chloroform is commercially available. It is more easily produced and less expensive than deuterated dichloromethane. Deuterochloroform is produced by the reaction of hexachloroacetone with deuterium oxide, using pyridine as a catalyst. The large difference in boiling points between the starting material and product facilitate purification by distillation. : Treating chloral with sodium deuteroxide (NaOD) gives deuterated chloroform. NMR solvent In proton NMR spectroscopy, deuterated solvent (enriched to >99% deuterium) is typically used to avoid recording a large interfering signal or signals from the proton(s) (i.e., hydrogen-1) present in the solvent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CF3CO2H
Trifluoroacetic acid (TFA) is a synthetic organofluorine compound with the chemical formula CF3CO2H. It belongs to the subclass of per- and polyfluoroalkyl substances (PFASs) known as ultrashort-chain perfluoroalkyl acids (PFAAs). TFA is not produced biologically or abiotically and is commonly used in organic chemistry for various purposes. It is the most abundant PFAS found in the environment. It is a haloacetic acid, with all three of the acetyl group's hydrogen atoms replaced by fluorine atoms. It is a colorless liquid with a vinegar-like odor. TFA is a stronger acid than acetic acid, having an acid ionisation constant, ''K''a, that is approximately 34,000 times higher, as the highly electronegative fluorine atoms and consequent electron-withdrawing nature of the trifluoromethyl group weakens the oxygen-hydrogen bond (allowing for greater acidity) and stabilises the anionic conjugate base. Synthesis TFA is prepared industrially by the electrofluorination of acetyl chlo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
C6F6
Hexafluorobenzene, HFB or perfluorobenzene is an organofluorine compound with the chemical formula . In this derivative of benzene, all hydrogen atoms have been replaced by fluorine atoms. The technical uses of the compound are limited, although it has some specialized uses in the laboratory owing to distinctive spectroscopic properties. Geometry of the aromatic ring Hexafluorobenzene stands somewhat aside in the perhalogenbenzenes. If a perhalogenated benzene ring were to remain planar, then geometric constraints would force adjacent halogens closer than their associated nonbonding radius. Consequently the benzene ring buckles, reducing Atomic orbital, ''p''-orbital overlap and aromaticity to avoid the steric clash. Perfluorobenzene is an exception: as shown in the following table, two fluorines are small enough to avoid collision, retaining planarity and full aromaticity. Synthesis The direct synthesis of hexafluorobenzene from benzene and fluorine has not been useful. I ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trifluorotoluene
Trifluorotoluene is an organic compound with the formula of C6H5CF3. This colorless fluorocarbon is used as a specialty solvent in organic synthesis and an intermediate in the production of pesticides and pharmaceuticals.Banks, R.E. Organofluorine Chemicals and their Industrial Applications, Ellis Horwood LTD, Chichester, 1979. Synthesis For small-scale laboratory preparations, trifluorotoluene is synthesized by coupling an aromatic halide and trifluoromethyl iodide in the presence of a copper catalyst: :PhX + CF3I → PhCF3 (where X = I, Br) Industrial production is done by reacting benzotrichloride with hydrogen fluoride in a pressurized reactor.Siegemund, Günter "Aromatic Compounds with Fluorinated Side-Chains" in Ullmann’s Encyclopedia of Industrial Chemistry 2005, Wiley-VCH. . :PhCCl3 + 3 HF → PhCF3 + 3 HCl Uses Trifluorotoluene has a variety of niche uses. Low toxicity alternative to dichloromethane According to Ogawa and Curran, trifluorotoluene is similar to d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
C6H5F
Fluorobenzene is an aryl fluoride and the simplest of the fluorobenzenes, with the formula C6H5F, often abbreviated Phenyl group, PhF. A colorless liquid, it is a precursor to many fluorophenyl compounds. Preparation PhF was first reported in 1886 by O. Wallach at the University of Bonn, who prepared the compound in two steps. Phenyldiazonium chloride was first converted to a triazene using piperidine: :[PhN2]Cl + 2 (CH2)5NH → PhN=N-N(CH2)5 + [(CH2)5NH2]Cl The triazine was then cleaved with hydrofluoric acid: :PhN=N-N(CH2)5 + 2 HF → PhF + N2 + [(CH2)5NH2]F Historical note: in Wallach's era, the element fluorine was symbolized with "Fl". Thus, his procedure is subtitled "Fluorbenzol, C6H5Fl". On the laboratory scale, PhF is prepared by the thermal decomposition of the benzenediazonium tetrafluoroborate: :PhN2BF4 → PhF + BF3 + N2 According to the procedure, solid [PhN2]BF4 is heated with a flame to initiate an exothermic reaction, which also affords bo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
