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Vinyl Halide
In organic chemistry, a vinyl halide is a compound with the formula CH2=CHX (X = halide). The term vinyl is often used to describe any alkenyl group. For this reason, alkenyl halides with the formula RCH=CHX are sometimes called vinyl halides. From the perspective of applications, the dominant member of this class of compounds is vinyl chloride, which is produced on the scale of millions of tons per year as a precursor to polyvinyl chloride. Polyvinyl fluoride is another commercial product. Related compounds include vinylidene chloride and vinylidene fluoride. Synthesis Vinyl chloride is produced by dehydrochlorination of 1,2-dichloroethane. Due to their high utility, many approaches to vinyl halides have been developed, such as: * reactions of vinyl organometallic species with halogens * Takai olefination * Stork-Zhao olefination - a modification of the Wittig reaction * Olefin metathesis Reactions Vinyl bromide and related alkenyl halides form the Grignard reagent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vinyl Halide
In organic chemistry, a vinyl halide is a compound with the formula CH2=CHX (X = halide). The term vinyl is often used to describe any alkenyl group. For this reason, alkenyl halides with the formula RCH=CHX are sometimes called vinyl halides. From the perspective of applications, the dominant member of this class of compounds is vinyl chloride, which is produced on the scale of millions of tons per year as a precursor to polyvinyl chloride. Polyvinyl fluoride is another commercial product. Related compounds include vinylidene chloride and vinylidene fluoride. Synthesis Vinyl chloride is produced by dehydrochlorination of 1,2-dichloroethane. Due to their high utility, many approaches to vinyl halides have been developed, such as: * reactions of vinyl organometallic species with halogens * Takai olefination * Stork-Zhao olefination - a modification of the Wittig reaction * Olefin metathesis Reactions Vinyl bromide and related alkenyl halides form the Grignard reagent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wittig Reaction
The Wittig reaction or Wittig olefination is a chemical reaction of an aldehyde or ketone with a triphenyl phosphonium ylide called a Wittig reagent. Wittig reactions are most commonly used to convert aldehydes and ketones to alkenes. Most often, the Wittig reaction is used to introduce a methylene group using methylenetriphenylphosphorane (Ph3P=CH2). Using this reagent, even a sterically hindered ketone such as camphor can be converted to its methylene derivative. Stereochemistry For the reaction with aldehydes, the double bond geometry is readily predicted based on the nature of the ylide. With unstabilised ylides (R3 = alkyl) this results in (''Z'')-alkene product with moderate to high selectivity. With stabilized ylides (R3 = ester or ketone), the (''E'')-alkene is formed with high selectivity. The (''E'')/(''Z'') selectivity is often poor with semistabilized ylides (R3 = aryl). To obtain the (''E'')-alkene for unstabilized ylides, the Schlosser modification of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heck Reaction
The Heck reaction (also called the Mizoroki–Heck reaction) is the chemical reaction of an unsaturated halide (or triflate) with an alkene in the presence of a base and a palladium catalyst (or palladium nanomaterial-based catalyst) to form a substituted alkene. It is named after Tsutomu Mizoroki and Richard F. Heck. Heck was awarded the 2010 Nobel Prize in Chemistry, which he shared with Ei-ichi Negishi and Akira Suzuki, for the discovery and development of this reaction. This reaction was the first example of a carbon-carbon bond-forming reaction that followed a Pd(0)/Pd(II) catalytic cycle, the same catalytic cycle that is seen in other Pd(0)-catalyzed cross-coupling reactions. The Heck reaction is a way to substitute alkenes. History The original reaction by Tsutomu Mizoroki (1971) describes the coupling between iodobenzene and styrene in methanol to form stilbene at 120 °C (autoclave) with potassium acetate base and palladium chloride catalysis. This work was an ex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stille Reaction
The Stille reaction is a chemical reaction widely used in organic synthesis. The reaction involves the coupling of two organic groups, one of which is carried as an organotin compound (also known as organostannanes). A variety of organic electrophiles provide the other coupling partner. The Stille reaction is one of many palladium-catalyzed coupling reactions.Hartwig, J. F. ''Organotransition Metal Chemistry, from Bonding to Catalysis''; University Science Books: New York, 2010. Stille, J. K. '' Angew. Chem. Int. Ed. Engl.'' 1986, ''25'', 508–524.ReviewFarina, V.; Krishnamurthy, V.; Scott, W. J. ''Org. React.'' 1998, ''50'', 1–652.Review : + \ \ce \ \overbrace^ + \!-\! :*\!,\ : Allyl, alkenyl, aryl, benzyl,acyl :*: halides (Cl, Br, I), pseudohalides (, OPO(OR)2), OAc The R1 group attached to the trialkyltin is normally sp2-hybridized, including vinyl, and aryl groups. These organostannanes are also stable to both air and moisture, and many of these reagents either are comm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Suzuki Reaction
The Suzuki reaction is an organic reaction, classified as a cross-coupling reaction, where the coupling partners are a boronic acid and an organohalide and the catalyst is a palladium, palladium(0) complex. It was first published in 1979 by Akira Suzuki (chemist), Akira Suzuki, and he shared the 2010 Nobel Prize in Chemistry with Richard F. Heck and Ei-ichi Negishi for their contribution to the discovery and development of palladium-catalyzed cross-couplings in organic synthesis. This reaction is also known as the Suzuki–Miyaura reaction or simply as the Suzuki coupling. It is widely used to organic synthesis, synthesize polyolefins, styrenes, and substituted biphenyls. Several reviews have been published describing advancements and the development of the Suzuki reaction. The general scheme for the Suzuki reaction is shown below, where a carbon-carbon single bond is formed by coupling a halide (R1-X) with an organoboron species (R2-BY2) using a palladium catalyst and a base (chemi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cross-coupling Reaction
In organic chemistry, a cross-coupling reaction is a reaction where two fragments are joined together with the aid of a metal catalyst. In one important reaction type, a main group organometallic compound of the type R-M (R = organic fragment, M = main group center) reacts with an organic halide of the type R'-X with formation of a new carbon–carbon bond in the product R-R'. Cross-coupling reaction are a subset of coupling reactions. It is often used in arylations. Richard F. Heck, Ei-ichi Negishi, and Akira Suzuki were awarded the 2010 Nobel Prize in Chemistry for developing palladium-catalyzed coupling reactions. Mechanism The mechanism generally involves reductive elimination of the organic substituents R and R' on a metal complex of the type LnMR(R') (where L is some arbitrary spectator ligand). The crucial intermediate LnMR(R') is formed in a two step process from a low valence precursor Ln. The oxidative addition of an organic halide (RX) to LnM gives LnMR(X). Sub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alkyne
\ce \ce Acetylene \ce \ce \ce Propyne \ce \ce \ce \ce 1-Butyne In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond. The simplest acyclic alkynes with only one triple bond and no other functional groups form a homologous series with the general chemical formula . Alkynes are traditionally known as acetylenes, although the name ''acetylene'' also refers specifically to , known formally as ethyne using IUPAC nomenclature. Like other hydrocarbons, alkynes are generally hydrophobic. Structure and bonding In acetylene, the H–C≡C bond angles are 180°. By virtue of this bond angle, alkynes are rod-like. Correspondingly, cyclic alkynes are rare. Benzyne cannot be isolated. The C≡C bond distance of 121 picometers is much shorter than the C=C distance in alkenes (134 pm) or the C–C bond in alkanes (153 pm). : The triple bond is very strong with a bond strength of 839 kJ/mol. The sigma bond contri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organolithium Reagent
In organometallic chemistry, organolithium reagents are chemical compounds that contain carbon–lithium (C–Li) bonds. These reagents are important in organic synthesis, and are frequently used to transfer the organic group or the lithium atom to the substrates in synthetic steps, through nucleophilic addition or simple deprotonation. Organolithium reagents are used in industry as an initiator for anionic polymerization, which leads to the production of various elastomers. They have also been applied in asymmetric synthesis in the pharmaceutical industry. Due to the large difference in electronegativity between the carbon atom and the lithium atom, the C−Li bond is highly ionic. Owing to the polar nature of the C−Li bond, organolithium reagents are good nucleophiles and strong bases. For laboratory organic synthesis, many organolithium reagents are commercially available in solution form. These reagents are highly reactive, and are sometimes pyrophoric. History and de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Grignard Reaction
The Grignard reaction () is an organometallic chemical reaction in which alkyl, allyl, vinyl, or aryl-magnesium halides (Grignard reagent) is added to a carbonyl group in an aldehyde or ketone. This reaction is important for the formation of carbon–carbon bonds. The reaction of an organic halide with magnesium is ''not'' a Grignard reaction, but provides a Grignard reagent. : Grignard reactions and reagents were discovered by and are named after the French chemist François Auguste Victor Grignard ( University of Nancy, France), who published it in 1900 and was awarded the 1912 Nobel Prize in Chemistry for this work. Reaction mechanism Because carbon is more electronegative than magnesium, the carbon attached to magnesium functions as a nucleophile and attacks the electrophilic carbon atom that is present within the polar bond of a carbonyl group. The addition of the Grignard reagent to the carbonyl typically proceeds through a six-membered ring transition state. Based ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Olefin Metathesis
Olefin metathesis is an organic reaction that entails the redistribution of fragments of alkenes (olefins) by the scission and regeneration of carbon-carbon double bonds. Because of the relative simplicity of olefin metathesis, it often creates fewer undesired by-products and hazardous wastes than alternative organic reactions. For their elucidation of the reaction mechanism and their discovery of a variety of highly active catalysts, Yves Chauvin, Robert H. Grubbs, and Richard R. Schrock were collectively awarded the 2005 Nobel Prize in Chemistry. Catalysts The reaction requires metal catalysts. Most commercially important processes employ heterogeneous catalysts. The heterogeneous catalysts are often prepared by in-situ activation of a metal halides (MClx) using organoaluminium or organotin compounds, e.g. combining MClx–EtAlCl2. A typical catalyst support is alumina. Commercial catalysts are often based on molybdenum and ruthenium. Well-defined organometallic compo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
