|
DABCO
DABCO (1,4-diazabicyclo .2.2ctane), also known as triethylenediamine or TEDA, is a bicyclic organic compound with the formula N2(C2H4)3. This colorless solid is a highly nucleophilic tertiary amine base, which is used as a catalyst and reagent in polymerization and organic synthesis. It is similar in structure to quinuclidine, but the latter has one of the nitrogen atoms replaced by a carbon atom. Regarding their structures, both DABCO and quinuclidine are unusual in that the methylene hydrogen atoms are eclipsed within each of the three ethylene linkages. Furthermore, the diazacyclohexane rings, of which there are three, adopt the boat conformations, not the usual chair conformations. Reactions The p''K''a of DABCOsup>+ (the protonated derivative) is 8.8, which is almost the same as ordinary alkylamines. The nucleophilicity of the amine is high because the amine centers are unhindered. It is sufficiently basic to promote a variety of coupling reactions. Catalyst DABCO is used ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Baylis–Hillman Reaction
In organic chemistry, the Baylis–Hillman, Morita–Baylis–Hillman, or MBH reaction is a coupling reaction, carbon–carbon bond-forming reaction between an electron-withdrawing group, activated alkene and a carbon electrophile in the presence of a nucleophilic catalyst, such as a tertiary amine or tertiary phosphine, phosphine. The product is densely functional group, functionalized, joining the alkene at the locant, α-position to a redox, reduced form of the electrophile (e.g. in the case of an aldehyde, an allylic alcohol (chemistry), alcohol). The reaction is named for Anthony B. Baylis and Melville E. D. Hillman, two of the chemists who developed the reaction at Celanese; and K. Morita, who published earlier work on the same. The MBH reaction offers several advantages in organic synthesis: # It combines easily prepared feedstock, starting materials with high atom economy. # It requires only mild conditions and does not require any transition metals. # Asym ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
F-TEDA-BF4
Selectfluor, a trademark of Air Products and Chemicals, is a reagent in chemistry that is used as a fluorine donor. This compound is a derivative of the nucleophillic base DABCO. It is a colourless salt that tolerates air and even water. It has been commercialized for use for electrophilic fluorination. Preparation : Selectfluor is synthesized by the ''N''-alkylation of diazabicyclo .2.2ctane (DABCO) with dichloromethane in a Menshutkin reaction, followed by ion exchange with sodium tetrafluoroborate (replacing the chloride counterion for the tetrafluoroborate). The resulting salt is treated with elemental fluorine and sodium tetrafluoroborate: The cation is often depicted with one skewed ethylene ((CH2)2) group. In fact, these pairs of CH2 groups are eclipsed so that the cation has idealized C3h symmetry. Mechanism of fluorination Electrophilic fluorinating reagents could in principle operate by electron transfer pathways or an SN2 attack at fluorine. This distinction has not ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bicyclic Molecule
A bicyclic molecule () is a molecule that features two joined rings. Bicyclic structures occur widely, for example in many biologically important molecules like α-thujene and camphor. A bicyclic compound can be carbocyclic (all of the ring atoms are carbons), or heterocyclic (the rings' atoms consist of at least two elements), like DABCO. Moreover, the two rings can both be aliphatic (''e.g.'' decalin and norbornane), or can be aromatic (''e.g.'' naphthalene), or a combination of aliphatic and aromatic (''e.g.'' tetralin). Three modes of ring junction are possible for a bicyclic compound: * In spiro compounds, the two rings share only one single atom, the spiro atom, which is usually a quaternary carbon. An example of a spirocyclic compound is the photochromic switch spiropyran. * In fused/condensed bicyclic compounds, two rings share two adjacent atoms. In other words, the rings share one covalent bond, ''i.e.'' the bridgehead atoms are directly connected (''e.g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quinuclidine
Quinuclidine is an organic compound with the formula . It is a bicyclic amine that can be viewed as a tied back version of triethylamine. It is a colorless solid. It is used as a reagent (base) and catalyst. It can be prepared by reduction of quinuclidone. Structure and chemical properties Regarding its structure, quinuclidine is unusual in that the methylene hydrogen atoms are eclipsed within each of the three ethylene linkages. Furthermore, the cyclohexane rings, of which there are three, adopt the boat conformations, not the usual chair conformations. Quinuclidine is a relatively strong organic base with p''K''a of the conjugate acid of 11.3. The basicity of other quinuclidines have been evaluated: 3-hydroxy- quinuclidine (9.9), 3-acetoxyquinuclidine (9.3), 3-chloroquinuclidine (8.9), DABCO (8.7), and 3-quinuclidone (7.2). It forms adducts with a variety of Lewis acids. Because of its compact structure, quinuclidine binds to trimethylborane more tightly than does tri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyurethane
Polyurethane (; often abbreviated PUR and PU) is a class of polymers composed of organic chemistry, organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethane term does not refer to the single type of polymer but a group of polymers. Unlike polyethylene and polystyrene, polyurethanes can be produced from a wide range of starting materials resulting in various polymers within the same group. This chemical variety produces polyurethanes with different chemical structures leading to many List of polyurethane applications, different applications. These include rigid and flexible foams, and coatings, adhesives, Potting (electronics), electrical potting compounds, and fibers such as spandex and polyurethane laminate (PUL). Foams are the largest application accounting for 67% of all polyurethane produced in 2016. A polyurethane is typically produced by reacting a polymeric isocyanate with a polyol. Since a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrophilic Fluorination
Electrophilic fluorination is the combination of a carbon-centered nucleophile with an electrophilic source of fluorine to afford organofluorine compounds. Although elemental fluorine and reagents incorporating an oxygen-fluorine bond can be used for this purpose, they have largely been replaced by reagents containing a nitrogen-fluorine bond. Electrophilic fluorination offers an alternative to nucleophilic fluorination methods employing alkali or ammonium fluorides and methods employing sulfur fluorides for the preparation of organofluorine compounds. Development of electrophilic fluorination reagents has always focused on removing electron density from the atom attached to fluorine; however, compounds containing nitrogen-fluorine bonds have proven to be the most economical, stable, and safe electrophilic fluorinating agents. Electrophilic N-F reagents are either neutral or cationic and may possess either sp2- or sp3-hybridized nitrogen. Although the precise mechanism of electrophil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Baylis Hilman Reaction Scheme
Baylis may refer to: Places *Baylis, Illinois, a village in Pike County, Illinois, United States *Baylis House, a manor house in Slough, England *Baylis Road, a road in Lambeth, London, England *Baylis & Harding, the handwash company based in Redditch, England *Baylis Street, one of the main shopping streets in Wagga Wagga, New South Wales, Australia *Baylis Court School, a girls' school in Slough, Berkshire, England Other uses *Baylis (surname) *Baylis–Hillman reaction, a reaction of an aldehyde and an α,β-unsaturated electron-withdrawing group catalyzed by DABCO (1,4-diazabicyclo .2.2ctane) to give an allylic alcohol *Aza-Baylis–Hillman reaction, the reaction of an α,β-unsaturated carbonyl compound with an imine in the presence of a nucleophile See also * Bayless, a surname *Bayliss Bayliss is a surname. Notable people with the surname include: * Adam Bayliss, film producer * Alfred Bayliss, American educational administrator * Brendan Bayliss, musician * David Bayliss, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluorescence Microscopy
A fluorescence microscope is an optical microscope that uses fluorescence instead of, or in addition to, scattering, reflection, and attenuation or absorption, to study the properties of organic or inorganic substances. A fluorescence microscope is any microscope that uses fluorescence to generate an image, whether it is a simple setup like an epifluorescence microscope or a more complicated design such as a confocal microscope, which uses optical sectioning to get better resolution of the fluorescence image. Principle The specimen is illuminated with light of a specific wavelength (or wavelengths) which is absorbed by the fluorophores, causing them to emit light of longer wavelengths (i.e., of a different color than the absorbed light). The illumination light is separated from the much weaker emitted fluorescence through the use of a spectral emission filter. Typical components of a fluorescence microscope are a light source (xenon arc lamp or mercury-vapor lamp are com ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogen Peroxide
Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscosity, viscous than Properties of water, water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3%–6% by weight) in water for consumer use and in higher concentrations for industrial use. Concentrated hydrogen peroxide, or "high-test peroxide", decomposes explosively when heated and has been used as both a monopropellant and an oxidizer in rocketry. Hydrogen peroxide is a reactive oxygen species and the simplest peroxide, a compound having an oxygen–oxygen single bond. It decomposes slowly into water and elemental oxygen when exposed to light, and rapidly in the presence of organic or reactive compounds. It is typically stored with a Stabilizer (chemistry), stabilizer in a weakly acidic solution in an opaque bottle. Hydrogen peroxide is found in biological systems including the human body. Enzymes that u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glycerol
Glycerol () is a simple triol compound. It is a colorless, odorless, sweet-tasting, viscous liquid. The glycerol backbone is found in lipids known as glycerides. It is also widely used as a sweetener in the food industry and as a humectant in pharmaceutical formulations. Because of its three hydroxyl groups, glycerol is miscible with water and is Hygroscopy, hygroscopic in nature. Modern use of the word glycerine (alternatively spelled glycerin) refers to commercial preparations of less than 100% purity, typically 95% glycerol. Structure Although chirality, achiral, glycerol is prochirality, prochiral with respect to reactions of one of the two primary alcohols. Thus, in substituted derivatives, the Glycerophospholipid#Nomenclature and stereochemistry, stereospecific numbering labels the molecule with a ''sn''- prefix before the stem name of the molecule. Production Natural sources Glycerol is generally obtained from plant and animal sources where it occurs in triglycerides, est ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
