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Decarbonylation
Decarbonylation is a type of organic reaction that involves loss of CO. It is often an undesirable reaction since it represents a degradation. In the chemistry of metal carbonyls, decarbonylation describes a substitution process, whereby a CO ligand is replaced by another ligand. Organic chemistry In the absence of metal catalysts, decarbonylation (vs decarboxylation) is rarely observed in organic chemistry. One exception is the decarbonylation of formic acid: :HCO2H → CO + H2O The reaction is induced by sulfuric acid, which functions as both a catalyst and a dehydrating agent. Via this reaction, formic acid is occasionally employed as a source of CO in the laboratory in lieu of cylinders of this toxic gas. With strong heating, formic acid and some of its derivatives may undergo decarbonylation, even without adding a catalyst. For instance, dimethylformamide slowly decomposes to give dimethylamine and carbon monoxide when heated to its boiling point (154 °C). Som ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tsuji–Wilkinson Decarbonylation Reaction
The Tsuji–Wilkinson decarbonylation reaction is a method for the decarbonylation of aldehydes and some acyl chlorides. The reaction name recognizes , whose team first reported the use of Wilkinson's catalyst (RhCl(PPh3)3) for these reactions: :RC(O)X + RhCl(PPh3)3 → RX + RhCl(CO)(PPh3)2 + PPh3 Although decarbonylation can be effected by several transition metal complexes, Wilkinson's catalyst has proven the most effective. Reaction mechanism Strictly speaking, this reaction results in the formation of a rhodium carbonyl complex rather than free carbon monoxide. The catalytic cycle is assumed to involve oxidative addition of the aldehyde (or acid chloride) to gives a 16e acyl Rh(III)-hydride intermediate, which undergoes migratory extrusion of CO proceed to form an 18-electron d6 Rh(III) carbonyl complex. Reductive elimination produces the decarbonylated product. In the catalytic variant of the Tsuji–Wilkinson decarbonylation, RhCl(CO)(PPh3)2 evolves CO above ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metal Carbonyl
Metal carbonyls are coordination complexes of transition metals with carbon monoxide ligands. Metal carbonyls are useful in organic synthesis and as catalysts or catalyst precursors in homogeneous catalysis, such as hydroformylation and Reppe chemistry. In the Mond process, nickel tetracarbonyl is used to produce pure nickel. In organometallic chemistry, metal carbonyls serve as precursors for the preparation of other organometallic complexes. Metal carbonyls are toxic by skin contact, inhalation or ingestion, in part because of their ability to carbonylate hemoglobin to give carboxyhemoglobin, which prevents the binding of oxygen. Nomenclature and terminology The nomenclature of the metal carbonyls depends on the charge of the complex, the number and type of central atoms, and the number and type of ligands and their binding modes. They occur as neutral complexes, as positively-charged metal carbonyl cations or as negatively charged metal carbonylates. The carbon monoxide liga ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organic Synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one of the most important branches of organic chemistry. There are several main areas of research within the general area of organic synthesis: ''total synthesis'', ''semisynthesis'', and ''methodology''. Total synthesis A total synthesis is the complete chemical synthesis of complex organic molecules from simple, commercially available petrochemical or natural precursors. Total synthesis may be accomplished either via a linear or convergent approach. In a ''linear'' synthesis—often adequate for simple structures—several steps are performed one after another until the molecule is complete; the chemical compounds made in each step are called synthetic intermediates. Most often, each step in a synthesis refers to a separate rea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vaska's Complex
Vaska's complex is the trivial name for the chemical compound ''trans''-carbonylchlorobis(triphenylphosphine)iridium(I), which has the formula IrCl(CO) (C6H5)3sub>2. This square planar diamagnetic organometallic complex consists of a central iridium atom bound to two mutually ''trans'' triphenylphosphine ligands, carbon monoxide and a chloride ion. The complex was first reported by J. W. DiLuzio and Lauri Vaska in 1961. Vaska's complex can undergo oxidative addition and is notable for its ability to bind to O2 reversibly. It is a bright yellow crystalline solid. Preparation The synthesis involves heating virtually any iridium chloride salt with triphenylphosphine and a carbon monoxide source. The most popular method uses dimethylformamide (DMF) as a solvent, and sometimes aniline is added to accelerate the reaction. Another popular solvent is 2-methoxyethanol. The reaction is typically conducted under nitrogen. In the synthesis, triphenylphosphine serves as both a ligand and a r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heme Oxygenase
Heme oxygenase, or haem oxygenase, (HMOX, commonly abbreviated as HO) is an enzyme that catalyzes the degradation of heme to produce biliverdin, ferrous ion, and carbon monoxide. There are many heme degrading enzymes in nature. In general, only aerobic heme degrading enzymes are referred to as HMOX-like enzymes whereas anaerobic enzymes are typically not affiliated with the HMOX family. Heme oxygenase Heme oxygenase (alternatively spelled using haem or oxidase) catalyzes the degradation of heme to biliverdin/bilirubin, ferrous ion, and carbon monoxide. The human genome may encode three isoforms of HMOX. The degradation of heme forms three distinct chromogens as seen in healing cycle of a bruise. This reaction can occur in virtually every cell and platelet; the classic example is the healing process of a contusion, which forms different chromogens as it gradually heals: (red) heme to (green) biliverdin to (yellow) bilirubin which is widely known for jaundice. In general, aside ... [...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 contribute ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclobutene
Cyclobutene is a cycloalkene. It is of interest in research but currently has no practical applications. It is a colorless easily condensed gas. A modern synthesis involves the 2-step dehydration of cyclobutanol. The compound was first prepared by thermolysis of the ammonium salt 4H7NMe3H. Cyclobutene thermally isomerizes to 1,3-butadiene. This strongly exothermic reaction reflects the dominance of ring strain. In contrast, the corresponding equilibrium for hexafluorocyclobutene disfavors hexafluorobutadiene. See also * Cyclobutane * Cyclobutadiene * Cyclobutyne * Squaric acid Squaric acid, also called quadratic acid because its four carbon atoms approximately form a square, is a diprotic organic acid with the chemical formula C4O2(OH)2. The conjugate base of squaric acid is the hydrogensquarate anion ; and the conjug ... References Monomers {{hydrocarbon-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclopropenone
Cyclopropenone is an organic compound with molecular formula C3H2O consisting of a cyclopropene carbon framework with a ketone functional group. It is a colorless, volatile liquid that boils near room temperature. Neat cyclopropenone polymerizes upon standing at room temperature. The chemical properties of the compound are dominated by the strong polarization of the carbonyl group, which gives a partial positive charge with aromatic stabilization on the ring and a partial negative charge on oxygen. It is an aromatic compound. See also * Diphenylcyclopropenone * Deltic acid *Tropone Tropone or 2,4,6-cycloheptatrien-1-one is an organic compound with some importance in organic chemistry as a non-benzenoid aromatic. The compound consists of a ring of seven carbon atoms with three conjugated alkene groups and a ketone group. Th ... References {{Molecules detected in outer space Enones Simple aromatic rings Cyclopropenes Non-benzenoid aromatic carbocycles ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hexaphenylbenzene
Hexaphenylbenzene is an aromatic compound composed of a benzene ring substituted with six phenyl rings. It is a colorless solid. The compound is the parent member of a wider class of hexaarylbenzenes, which are mainly of theoretical interest. Preparation It is prepared by heating tetraphenylcyclopentadienone and diphenylacetylene in benzophenone or other high-temperature solvent. The reaction proceeds via a Diels-Alder reaction to give the hexaphenyldienone, which then eliminates carbon monoxide. : Together with 1,2,3,4-tetraphenylnaphthalene, hexaphenylbenzene forms by the chromium-catalyzed oligomerization of diphenylacetylene Diphenylacetylene is the chemical compound C6H5C≡CC6H5. The molecule consists of two phenyl groups attached to a C2 unit. A colorless solid, it is used as a building block in organic synthesis and as a ligand in organometallic chemistry. Prepar .... Structure The stable conformation of this molecule has the phenyl rings rotated out of the plane ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ï€ Bond
In chemistry, pi bonds (π bonds) are covalent chemical bonds, in each of which two lobes of an orbital on one atom overlap with two lobes of an orbital on another atom, and in which this overlap occurs laterally. Each of these atomic orbitals has an electron density of zero at a shared nodal plane that passes through the two bonded nuclei. This plane also is a nodal plane for the molecular orbital of the pi bond. Pi bonds can form in double and triple bonds but do not form in single bonds in most cases. The Greek letter π in their name refers to p orbitals, since the orbital symmetry of the pi bond is the same as that of the p orbital when seen down the bond axis. One common form of this sort of bonding involves p orbitals themselves, though d orbitals also engage in pi bonding. This latter mode forms part of the basis for metal-metal multiple bonding. Pi bonds are usually weaker than sigma bonds. The C-C double bond, composed of one sigma and one pi bond, has a bo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cheletropic Reaction
In organic chemistry, cheletropic reactions, also known as chelotropic reactions, IUPAC GoldBook are a type of pericyclic reaction (a chemical reaction that involves a transition state with a Ring (chemistry), cyclic array of atoms and an associated cyclic array of interacting Atomic orbital, orbitals).Eric V. Anslyn and Dennis A. Dougherty ''Modern Physical Organic Chemistry'' University Science Books, 2006. Specifically, cheletropic reactions are a subclass of cycloadditions. The key distinguishing feature of cheletropic reactions is that on one of the reagents, both new bonds are being made to the same atom.Ian Fleming. ''Frontier Orbitals and Organic Chemistry Reactions.'' Wiley, 1976. Theoretical analysis In the pericyclic transition state, a small molecu ...[...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ketone
In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bond C=O). The simplest ketone is acetone (where R and R' is methyl), with the formula . Many ketones are of great importance in biology and in industry. Examples include many sugars (ketoses), many steroids (e.g., testosterone), and the solvent acetone. Nomenclature and etymology The word ''ketone'' is derived from ''Aketon'', an old German word for ''acetone''. According to the rules of IUPAC nomenclature, ketone names are derived by changing the suffix ''-ane'' of the parent alkane to ''-anone''. Typically, the position of the carbonyl group is denoted by a number, but traditional nonsystematic names are still generally used for the most important ketones, for example acetone and benzophenone. These nonsystematic names are considere ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
