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Fluorination By Sulfur Tetrafluoride
Fluorination by sulfur tetrafluoride produces organofluorine compounds from oxygen-containing organic functional groups using sulfur tetrafluoride. The reaction has broad scope, and SF4 is an inexpensive reagent. It is however hazardous gas whose handling requires specialized apparatus. Thus, for many laboratory scale fluorinations diethylaminosulfur trifluoride ("DAST") is used instead. Main functional group conversions Carboxylic acids, amides, esters, and carboxylate salts convert to the trifluoromethyl derivatives, although conditions vary widely: : For carboxlic acids, the first step gives the acyl fluorides, in keeping with the tendency of SF4 to fluorinate acidic hydroxyl groups: : Similarly SF4 converts sulfonic acids to sulfonyl fluorides: : Aldehydes and ketones convert to geminal difluorides: : Alcohols convert to alkyl fluorides, although this conversion works best with acidic alcohols, such as fluorinated alcohols: : Mechanism The mechanism of fluorination by SF4 i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organofluorine Compound
Organofluorine chemistry describes the chemistry of the organofluorines, organic compounds that contain the carbon–fluorine bond. Organofluorine compounds find diverse applications ranging from oil and water repellents to pharmaceuticals, refrigerants, and reagents in catalysis. In addition to these applications, some organofluorine compounds are pollutants because of their contributions to ozone depletion, global warming, bioaccumulation, and toxicity. The area of organofluorine chemistry often requires special techniques associated with the handling of fluorinating agents. The carbon–fluorine bond Fluorine has several distinctive differences from all other substituents encountered in organic molecules. As a result, the physical and chemical properties of organofluorines can be distinctive in comparison to other organohalogens. # The carbon–fluorine bond is one of the strongest in organic chemistry (an average bond energy around 480 kJ/molKirsch, Peer ''Modern flu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sulfur Tetrafluoride
Sulfur tetrafluoride is the chemical compound with the formula S F4. It is a colorless corrosive gas that releases dangerous HF upon exposure to water or moisture. Despite these unwelcome characteristics, this compound is a useful reagent for the preparation of organofluorine compounds, some of which are important in the pharmaceutical and specialty chemical industries. Structure Sulfur in SF4 is in the formal +4 oxidation state. Of sulfur's total of six valence electrons, two form a lone pair. The structure of SF4 can therefore be anticipated using the principles of VSEPR theory: it is a see-saw shape, with S at the center. One of the three equatorial positions is occupied by a nonbonding lone pair of electrons. Consequently, the molecule has two distinct types of F ligands, two axial and two equatorial. The relevant bond distances are = 164.3 pm and = 154.2 pm. It is typical for the axial ligands in hypervalent molecules to be bonded less strongl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diethylaminosulfur Trifluoride
Diethylaminosulfur trifluoride (DAST) is the organosulfur compound with the formula Et2NSF3. This liquid is a fluorinating reagent used for the synthesis of organofluorine compounds. The compound is colourless; older samples assume an orange colour. Use in organic synthesis DAST converts alcohols to the corresponding alkyl fluorides as well as aldehydes and unhindered ketones to geminal difluorides. Carboxylic acids react no further than the acyl fluoride (sulfur tetrafluoride effects the transformation —CO2H → —CF3). DAST is used in preference to the more classical gaseous SF4, since as a liquid it is more easily handled. A slightly thermally more stable compound is morpho-DAST. Acid-labile substrates are less likely to undergo rearrangement and elimination since DAST is less prone to contamination with acids. Reaction temperatures are milder as well – alcohols typically react at −78 °C and ketones around 0 °C. Synthesis DAST is prepared by the reaction of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trifluoromethyl
The trifluoromethyl group is a functional group that has the formula -CF3. The naming of is group is derived from the methyl group (which has the formula -CH3), by replacing each hydrogen atom by a fluorine atom. Some common examples are trifluoromethane H–, 1,1,1-trifluoroethane –, and hexafluoroacetone –CO–. Compounds with this group are a subclass of the organofluorines. Properties The trifluoromethyl group has a significant electronegativity that is often described as being intermediate between the electronegativities of fluorine and chlorine. For this reason, trifluoromethyl-substituted compounds are often strong acids, such as trifluoromethanesulfonic acid and trifluoroacetic acid. Conversely, the trifluoromethyl group lowers the basicity of compounds like trifluoroethanol. Uses The trifluoromethyl group occurs in certain pharmaceuticals, drugs, and abiotically synthesized natural fluorocarbon based compounds. The medicinal use of the trifloromethyl group dates ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sulfonyl Halide
In inorganic chemistry, sulfonyl halide groups occur when a sulfonyl () functional group is singly bonded to a halogen atom. They have the general formula , where X is a halogen. The stability of sulfonyl halides decreases in the order fluorides > chlorides > bromides > iodides, all four types being well known. The sulfonyl chlorides and fluorides are of dominant importance in this series. Structure Sulfonyl halides have tetrahedral sulfur centres attached to two oxygen atoms, an organic radical, and a halide. In a representative example, methanesulfonyl chloride, the S=O, S−C, and S−Cl bond distances are respectively 142.4, 176.3, and 204.6 pm. Sulfonyl chlorides Sulfonic acid chlorides, or sulfonyl chlorides, are a sulfonyl halide with the general formula . Production Arylsulfonyl chlorides are made industrially in a two-step, one-pot reaction from an arene (in this case, benzene) and chlorosulfuric acid: :C6H6 + HOSO2Cl -> C6H5SO3H + HCl :C6H5SO3H + HOSO2Cl -> ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phosphorus Pentachloride
Phosphorus pentachloride is the chemical compound with the formula PCl5. It is one of the most important phosphorus chlorides, others being PCl3 and POCl3. PCl5 finds use as a chlorinating reagent. It is a colourless, water-sensitive and moisture-sensitive solid, although commercial samples can be yellowish and contaminated with hydrogen chloride. Structure The structures for the phosphorus chlorides are invariably consistent with VSEPR theory. The structure of PCl5 depends on its environment. Gaseous and molten PCl5 is a neutral molecule with trigonal bipyramidal geometry and (''D''3h) symmetry. The hypervalent nature of this species (as well as of , see below) can be explained with the inclusion of non-bonding molecular orbitals (molecular orbital theory) or resonance (valence bond theory). This trigonal bipyramidal structure persists in nonpolar solvents, such as CS2 and CCl4. In the solid state PCl5 is an ionic compound, formulated . In solutions of polar solvents ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogen Fluoride
Hydrogen fluoride (fluorane) is an inorganic compound with the chemical formula . This colorless gas or liquid is the principal industrial source of fluorine, often as an aqueous solution called hydrofluoric acid. It is an important feedstock in the preparation of many important compounds including pharmaceuticals and polymers, e.g. polytetrafluoroethylene (PTFE). HF is widely used in the petrochemical industry as a component of superacids. Hydrogen fluoride boils at near room temperature, much higher than other hydrogen halides. Hydrogen fluoride is an extremely dangerous gas, forming corrosive and penetrating hydrofluoric acid upon contact with moisture. The gas can also cause blindness by rapid destruction of the corneas. History In 1771 Carl Wilhelm Scheele prepared the aqueous solution, hydrofluoric acid in large quantities, although hydrofluoric acid had been known in the glass industry before then. French chemist Edmond Frémy (1814–1894) is credited with disco ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amino Acid
Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha amino acids appear in the genetic code. Amino acids can be classified according to the locations of the core structural functional groups, as Alpha and beta carbon, alpha- , beta- , gamma- or delta- amino acids; other categories relate to Chemical polarity, polarity, ionization, and side chain group type (aliphatic, Open-chain compound, acyclic, aromatic, containing hydroxyl or sulfur, etc.). In the form of proteins, amino acid ''residues'' form the second-largest component ( water being the largest) of human muscles and other tissues. Beyond their role as residues in proteins, amino acids participate in a number of processes such as neurotransmitter transport and biosynthesis. It is thought that they played a key role in enabling li ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
