The halogens are a group in the periodic table consisting of six chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and the radioactive elements astatine (At) and tennessine (Ts), though some authors would exclude tennessine as its chemistry is unknown and is theoretically expected to be more like that of gallium. In the modern IUPAC nomenclature, this group is known as group 17.
In organic chemistry, an imine is a functional group or organic compound containing a carbon–nitrogen double bond. The nitrogen atom can be attached to a hydrogen or an organic group (R). The carbon atom has two additional single bonds. Imines are common in synthetic and naturally occurring compounds and they participate in many reactions.
In organic chemistry, an aryl halide is an aromatic compound in which one or more hydrogen atoms, directly bonded to an aromatic ring are replaced by a halide. The haloarene are different from haloalkanes because they exhibit many differences in methods of preparation and properties. The most important members are the aryl chlorides, but the class of compounds is so broad that there are many derivatives and applications.
Chemoselectivity is the preferential reaction of a chemical reagent with one of two or more different functional groups.
Nickel(II) fluoride is the chemical compound with the formula NiF2. It is an ionic compound of nickel and fluorine and forms yellowish to green tetragonal crystals. Unlike many fluorides, NiF2 is stable in air.
Dioxygen difluoride is a compound of fluorine and oxygen with the molecular formula O2F2. It can exist as an orange-colored solid which melts into a red liquid at −163 °C (110 K). It is an extremely strong oxidant and decomposes into oxygen and fluorine even at −160 °C (113 K) at a rate of 4% per day — its lifetime at room temperature is thus extremely short. Dioxygen difluoride reacts vigorously with nearly every chemical it encounters (including ordinary ice) leading to its onomatopoeic nickname FOOF (a play on its chemical structure and its explosive tendencies).
Tetrazoles are a class of synthetic organic heterocyclic compound, consisting of a 5-member ring of four nitrogen atoms and one carbon atom. The name tetrazole also refers to the parent compound with formula CH2N4, of which three isomers can be formulated.
Fluoroform, or trifluoromethane, is the chemical compound with the formula CHF3. It is a hydrofluorocarbon as well as being apart of the haloforms, a class of compounds with the formula CHX3 with C3v symmetry. Fluoroform is used in diverse applications in organic synthesis. It is not an ozone depleter but is a greenhouse gas.
A halonium ion is any onium ion containing a halogen atom carrying a positive charge. This cation has the general structure R−+X−R′ where X is any halogen and no restrictions on R, this structure can be cyclic or an open chain molecular structure. Halonium ions formed from fluorine, chlorine, bromine, and iodine are called fluoronium, chloronium, bromonium, and iodonium, respectively. The 3-membered cyclic variety commonly proposed as intermediates in electrophilic halogenation may be called haliranium ions, using the Hantzsch-Widman nomenclature system.
The Ramberg–Bäcklund reaction is an organic reaction converting an α-halo sulfone into an alkene in presence of a base with extrusion of sulfur dioxide. The reaction is named after the two Swedish chemists Ludwig Ramberg and Birger Bäcklund. The carbanion formed by deprotonation gives an unstable episulfone that decomposes with elimination of sulfur dioxide. This elimination step is considered to be a concerted cheletropic extrusion.
In inorganic chemistry, sulfonyl halide groups occur when a sulfonyl functional group is singly bonded to a halogen atom. They have the general formula RSO2X, 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.
Takai olefination in organic chemistry describes the organic reaction of an aldehyde with a diorganochromium compound to form an alkene. It is a name reaction, named for Kazuhiko Takai, who first reported it in 1986. In the original reaction, the organochromium species is generated from iodoform or bromoform and an excess of chromium(II) chloride and the product is a vinyl halide. One main advantage of this reaction is the E-configuration of the double bond that is formed. According to the original report, existing alternatives such as the Wittig reaction only gave mixtures.
Vanadium(V) fluoride is the inorganic compound with the chemical formula VF5. It is a colorless volatile liquid that freezes near room temperature. It is a highly reactive compound, as indicated by its ability to fluorinate organic substances.
In chemistry, molecular oxohalides (oxyhalides) are a group of chemical compounds in which both oxygen and halogen atoms are attached to another chemical element A in a single molecule. They have the general formula AOmXn, where X is a halogen. Known oxohalides have fluorine (F), chlorine (Cl), bromine (Br), and/or iodine (I) in their molecules. The element A may be a main group element, a transition element, a rare earth element or an actinide. The term oxohalide, or oxyhalide, may also refer to minerals and other crystalline substances with the same overall chemical formula, but having an ionic structure.
Cyclopentadienyliron dicarbonyl dimer is an organometallic compound with the formula [(η5-C5H5)Fe(CO)2]2, often abbreviated to Cp2Fe2(CO)4, [CpFe(CO)2]2 or even Fp2, with the colloquial name "fip dimer". It is a dark reddish-purple crystalline solid, which is readily soluble in moderately polar organic solvents such as chloroform and pyridine, but less soluble in carbon tetrachloride and carbon disulfide. Cp2Fe2(CO)4 is insoluble in but stable toward water. Cp2Fe2(CO)4 is reasonably stable to storage under air and serves as a convenient starting material for accessing other Fp (CpFe(CO)2) derivatives (described below).
Hydrodefluorination (HDF) is a type of organic reaction in which in a substrate of a carbon–fluorine bond is replaced by a carbon–hydrogen bond. The topic is of some interest to scientific research. In one general strategy for the synthesis of fluorinated compounds with a specific substitution pattern, the substrate is a cheaply available perfluorinated hydrocarbon. An example is the conversion of hexafluorobenzene (C6F6) to pentafluorobenzene (C6F5H) by certain zirconocene hydrido complexes. In this type of reaction the thermodynamic driving force is the formation of a metal-fluorine bond that can offset the cleavage of the very stable C-F bond. Other substrates that have been investigated are fluorinated alkenes. Another reaction type is oxidative addition of a metal into a C-F bond followed by a reductive elimination step in presence of a hydrogen source. For example, perfluorinated pyridine reacts with bis(cyclooctadiene)nickel(0) and triethylphosphine to the oxidative addition product and then with HCl to the ortho-hydrodefluorinated product. In reductive hydrodefluorination the fluorocarbon is reduced in a series of single electron transfer steps through the radical anion, the radical and the anion with ultimate loss of a fluorine anion. An example is the conversion of pentafluorobenzoic acid to 3,4,5-tetrafluorobenzoic acid in a reaction of zinc dust in aqueous ammonia.
In organic chemistry, a vinyl iodide functional group is an alkene with one or more iodide substituents. Vinyl iodides are versatile molecules that serve as important building blocks and precursors in organic synthesis. They are commonly used in carbon-carbon forming reactions in transition-metal catalyzed cross-coupling reactions, such as Stille reaction, Heck reaction, Sonogashira coupling, and Suzuki coupling. Synthesis of well-defined geometry or complexity vinyl iodide is important in stereoselective synthesis of natural products and drugs.
The fluorosulfates or fluorosulfonates are a set of salts of fluorosulfuric acid with an ion formula SO3F−. The fluorosulfate anion can be treated as though it were a hydrogen sulfate anion with hydroxyl substituted by fluorine. The fluorosulfate ion has a low propensity to form complexes with metal cations. Since fluorine is similar in size to oxygen, the fluorosulfate ion is roughly tetrahedral and forms salts similar to those of the perchlorate ion. It is isoelectronic with sulfate, SO4−2. When an organic group is substituted for the anions, organic fluorosulfonates are formed.
David Markham Lemal is the Albert W. Smith Professor of Chemistry Emeritus and Research Professor of Chemistry at Dartmouth College. He received an A.B. degree (summa) from Amherst College in 1955 and a Ph.D. in chemistry from Harvard University in 1959. At Harvard he worked with R. B. Woodward on deoxy sugars and a synthesis of the alkaloid yohimbine.
Alan K. Brisdon is a British chemist and a Senior Lecturer in the Department of Chemistry at The University of Manchester. His research in general is based on fluorine chemistry, including on HCFCs, fluorine-containing organometallic systems, fluorophosphines and fluorine-containing materials, such as ionic liquids and fluorographenes.
