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In organic chemistry, 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. [ 1 ] [ 2 ] Because of the relative simplicity of olefin metathesis, it often creates fewer undesired by-products and hazardous wastes than alternative ...
Chauvin's work centred on metathesis, which involves organic (carbon-based) compounds. In metathesis, chemists break double bonds more easily by introducing a catalyst—that is, a substance that starts or speeds up a chemical reaction. Chemists began performing metathesis in the 1950s without knowing exactly how the reaction worked.
The metal-mediated processes include a carbonyl-olefination and an olefin–olefin metathesis event. There are two general mechanistic schemes to perform this overall transformation: one, reaction of a [M=CHR 1] reagent with an alkene to generate a new metal alkylidene, which then couples with a carbonyl group to form the desired substituted alkene and an inactive [M=O] species (type A); two ...
At MIT Schrock was the first to elucidate the structure and mechanism of so-called 'black box' olefin metathesis catalysts. He showed that the alpha abstraction reaction could be used to prepare molybdenum or tungsten alkylidene and alkylidyne complexes in large variety through ligand variations.
The 2-butenes are then subjected to metathesis with ethylene. Rhenium- and molybdenum-containing heterogeneous catalysis are used. Nowadays, only the "reverse" reaction is practiced, i.e., the conversion of ethylene and 2-butene to propylene: [2] CH 2 =CH 2 + CH 3 CH=CHCH 3 → 2 CH 2 =CHCH 3
The mechanism of homogeneous ring-opening metathesis polymerization is well-studied. It is similar to any olefin metathesis reaction. Initiation occurs by forming an open coordination site on the catalyst. Propagation happens via a metallacycle intermediate formed after a 2+2 cycloaddition. When using a G3 catalyst, 2+2 cycloaddition is the ...
Ring-closing metathesis (RCM) is a widely used variation of olefin metathesis in organic chemistry for the synthesis of various unsaturated rings via the intramolecular metathesis of two terminal alkenes, which forms the cycloalkene as the E-or Z-isomers and volatile ethylene. [1] [2]
In organometallic chemistry, a metallacycle is a derivative of a carbocyclic compound wherein a metal has replaced at least one carbon center; [2] [3] this is to some extent similar to heterocycles. Metallacycles appear frequently as reactive intermediates in catalysis, e.g. olefin metathesis and alkyne trimerization.