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Encyclopedia > Olefin metathesis

Olefin metathesis or transalkylidenation (in some literature, a disproportionation) is an organic reaction which involves redistribution of olefinic (alkene) bonds. Since its discovery, olefin metathesis has gained widespread use in research and industry for making products ranging from medicines and polymers to enhanced fuels. Its advantages include the creation of fewer sideproducts and hazardous wastes. Yves Chauvin, Robert H. Grubbs, Richard R. Schrock shared the 2005 Nobel Prize in Chemistry for "the development of the metathesis method in organic synthesis". jfkdjdfdfd--69. ... Organic reactions are chemical reactions between organic compounds. ... A synonym for the more widely accepted term, alkene. ... An alkene in organic chemistry is an unsaturated hydrocarbon containing at least one carbon-carbon double bond. ... A chemical bond is the phenomenon of atoms being held together in molecules or crystals. ... Research is an active, diligent, and systematic process of inquiry in order to discover, interpret or revise facts, events, behaviours, or theories, or to make practical applications with the help of such facts, laws, or theories. ... Medicine on the Web NLM (National Library of Medicine, contains resources for patients and healthcare professionals) Virtual Hospital (digital health sciences library by the University of Iowa) Online Medical Dictionary Collection of links to free medical resources Categories: Medicine | Health ... A polymer is a generic term used to describe a substantially long molecule. ... For the workstation, see SGI Fuel. ... Hazardous waste is waste that poses substantial or potential threats to public health or the environment and generally exhibits one or more of these characteristics: ignitability corrosivity reactivity (explosive) toxicity Generally, toxicity is quantified through the use of the Toxicity Characteristic Leaching Procedure or TCLP test, as required by EPA... Yves Chauvin (born October 10, 1930) is a French chemist and Nobel Prize winner. ... Professor Robert H. Grubbs (b. ... Richard R. Schrock was the recipient of the 2005 Nobel Prize in Chemistry for his contribution to the metathesis method in organic chemistry. ... 2005(MMV) is a common year starting on Saturday of the Gregorian calendar. ... List of Nobel Prize laureates in Chemistry from 1901 to the present day. ... Organic synthesis is the construction of organic molecules via chemical processes. ...


The reaction is catalyzed by metals such as nickel, tungsten, ruthenium and molybdenum. The reaction consists of an alkene double bond cleavage, followed by a statistical redistribution of alkylidene fragments. The general scope is outlined by the following equation: In chemistry and biology, catalysis is the acceleration of the reaction rate of a chemical reaction by means of a substance, called a catalyst, that is itself unchanged chemically by the overall reaction. ... For alternative meanings see metal (disambiguation). ... General Name, Symbol, Number nickel, Ni, 28 Chemical series transition metals Group, Period, Block 10, 4, d Appearance lustrous, metallic Atomic mass 58. ... General Name, Symbol, Number tungsten, W, 74 Chemical series transition metals Group, Period, Block 6, 6, d Appearance grayish white, lustrous Atomic mass 183. ... General Name, Symbol, Number ruthenium, Ru, 44 Chemical series transition metals Group, Period, Block 8, 5, d Appearance silvery white metallic Atomic mass 101. ... General Name, Symbol, Number molybdenum, Mo, 42 Chemical series transition metals Group, Period, Block 6, 5, d Appearance gray metallic Atomic mass 95. ... An alkene in organic chemistry is an unsaturated hydrocarbon containing at least one carbon-carbon double bond. ... Covalent bonding is a form of chemical bonding characterized by the sharing of one or more pairs of electrons between atoms, in order to produce a mutual attraction, which holds the resultant molecule together. ...

Contents

Image File history File links Metathesis. ...


Overview

Olefin metathesis was first used in petroleum reformation for the synthesis of higher olefins in the Shell higher olefin process (SHOP) under high pressure and high temperatures. Many traditional catalysts are derived from a reaction of the metal halides with alkylation agents for example WCl6-EtOH-EtAlCl2. A metathesis reaction is a chain reaction involving a metal-carbene. This carbene reacts with a olefine to a metallacyclobutane intermediate. Nodding donkey pumping an oil well near Sarnia, Ontario, 2001 Petroleum (from Greek petra – rock and oleum – oil), crude oil, sometimes colloquially called black gold, is a thick, dark brown or greenish liquid. ... In chemistry a carbene is a short-lived and highly reactive organic molecule with a divalent carbon atom with only 6 valence electrons and the general formula: R1R2C:. The carbon atom is sp2 hybridised with a empty p-orbital extending above and below a plane containing R1 and R2 and...

A metal carbene based on ruthenium is Grubbs' Catalyst[1], a Schrock carbene is a molybdenum catalyst. Image File history File links Metathesis_mechanism. ... Grubbs Catalyst is named after the chemist by whom it was first synthesized, Robert H. Grubbs. ...


Metathesis chemistry

The complete family of metathesis chemistry: In general, a chemical reaction is referred to as metathesis if it is of the type: A-B + C-D → A-D + C-B where parts of two reacting structures swap places. ...

  • Cross-metathesis (CM)
  • Ring-closing metathesis (RCM)
  • Enyne metathesis (EM)
  • Ring-opening metathesis (ROM)
  • Ring-opening metathesis polymerization (ROMP)
  • Acyclic diene metathesis (ADMET)
  • Alkyne metathesis (AM)
  • Alkane metathesis
  • Alkene metathesis

Like most organometallic reactions, the metathesis pathway is usually driven by a thermodynamic imperative; that is, the final products are determined by the energetics of the possible products, with a distribution of products proportional to the exponential of their respective energy values. The Mortreux system consists of molybdenum hexacarbonyl resorcinol catalyst system. ... In alkane metathesis acyclic alkanes are scrambled to higher and lower homologues with tantalum hydride supported on silica (SiO2)TaH at temperatures of 25 °C to 200 °C. In this reaction ethane is converted into methane, propane and traces of butane. ...


Alkene metathesis is generally driven by the evolution of gaseous ethylene; and alkyne metathesis is driven by the evolution of acetylene. These are both dominated by the entropy gained by the net release of gas. Enyne metathesis cannot evolve a simple gas, and for that reason is disfavored. Ring-opening metathesis usually involves a strained alkene (often a norbornene) and the release of ring strain drives the reaction. Ring-closing metathesis, conversely, usually involves the formation of a five- or six-membered ring which is highly energetically favorable; although these reactions tend to also evolve ethylene. RCM has been used to close larger macrocycles, in which case the reaction may be kinetically controlled by running the reaction at extreme dilutions. Ethylene or ethene is the simplest alkene hydrocarbon, consisting of two carbon atoms and four hydrogens. ... The chemical compound acetylene, also called ethyne, was discovered in 1836 by Edmund Davy, in England; its chemical formula is C2H2 and its structure is: Acetylene is a colorless and extremely flammable gas at standard temperature and pressure, with a melting point of -80. ... Norbornene or norbornylene or norcamphene is a bridged cyclic hydrocarbon. ... Ethylene or ethene is the simplest alkene hydrocarbon, consisting of two carbon atoms and four hydrogens. ...


Alkane metathesis is synthetically equivalent to ozonolysis followed by the Wittig reaction (or vice versa). In ozonolysis ozone cleaves an alkene into carbonyl compounds. ... The Wittig reaction is a chemical reaction of an aldehyde or ketone with a phosphonium ylide to give an alkene and triphenylphosphine oxide. ...


Examples

An example of enantioselective olefin metathesis: [2] In chemistry two stereoisomers are said to be enantiomers if one can be superimposed on the mirror image of the other. ... A synonym for the more widely accepted term, alkene. ...

The metathesis reaction of 1-hexene with the WCl4(OAr)2 catalyst yields 5-decene[3] plus many byproducts from secondary metathesis reactions. Image File history File links Metathesis_example. ...


External links

  • Olefin Metathesis: Big-Deal Reaction Chemical & Engineering News, December 23, 2002 Volume 80, Number 51 p. 29-33 [4]
  • Olefin Metathesis: The Early Days Chemical & Engineering News, December 23, 2002 Volume 80, Number 51 p. 34-38 [5]
  • Development of the metathesis method in organic synthesis Royal Swedish Academy of Sciences [6]

References

  1. ^ Ileana Dragutan*, Valerian Dragutan*, Petru Filip (2005). "Recent developments in design and synthesis of well-defined ruthenium metathesis catalysts – a highly successful opening for intricate organic synthesis". 105. From Arkivoc.
  2. ^ Joshua J. Van Veldhuizen, Steven B. Garber, Jason S. Kingsbury, and Amir H. Hoveyda J. (2002). "A Recyclable Chiral Ru Catalyst for Enantioselective Olefin Metathesis. Efficient Catalytic Asymmetric Ring-Opening/Cross Metathesis in Air". Am. Chem. Soc. 124 (18): 4954–4955. Abstract.
  3. ^ Ione M. Baibich, Carla Kern (2002). "Reactivity of Tungsten-aryloxides with Hydrosilane Cocatalysts in Olefin Metathesis". Journal of the Brazilian Chemical Society 13: 43. [7].

  Results from FactBites:
 
Olefin metathesis - Patent 4490512 (1870 words)
This process simplifies olefin metathesis as acetylenes can be handled in the atmosphere, while ethylaluminum dichloride or related materials which have been used in the past instantaneously ignite when exposed to the atmosphere.
According to the teachings of subject invention, olefin metathesis is accomplished by combining olefins and acetylenes and tungsten salts such as tungsten hexachloride.
Another object of subject invention is to accomplish olefin metathesis in a simplified manner wherein acetylenes used as coinitiators can be handled in the atmosphere, unlike the compounds such as ethylaluminum dichloride or related materials used in the prior art.
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