Acyclic diene metathesis mechanism

Industrial methods[ edit ] Alkenes are produced by hydrocarbon cracking. Raw materials are mostly natural gas condensate components principally ethane and propane in the US and Mideast and naphtha in Europe and Asia.

Acyclic diene metathesis mechanism

Industrial methods[ edit ] Alkenes are produced by hydrocarbon cracking. Raw materials are mostly natural gas condensate components principally ethane and propane in the US and Mideast and naphtha in Europe and Asia.

Alkanes are broken apart at high temperatures, often in the presence of a zeolite catalyst, to produce a mixture of primarily aliphatic alkenes and lower molecular weight alkanes.

The mixture is feedstock and temperature dependent, and separated by fractional distillation. This is mainly used for the manufacture of small alkenes up to six carbons. This process is also known as reforming. Both processes are endothermic and are driven towards the alkene at high temperatures by entropy.

Elimination reactions[ edit ] One of the principal methods for alkene synthesis in the laboratory is the room elimination of alkyl halides, alcohols, and similar compounds. Most E2 eliminations start with an alkyl halide or alkyl sulfonate ester such as a tosylate or triflate.

When an alkyl halide is used, the reaction is called a dehydrohalogenation.

Organic Chemistry Animations Welcome to the Introductory Page. This site contains interactive 3D animations for some of the most important organic reactions covered during an undergraduate degree. Organic Chemistry Animations Welcome to the Introductory Page. This site contains interactive 3D animations for some of the most important organic reactions covered during an undergraduate degree. 京都大学化学研究所 材料機能化学研究系 高分子制御合成領域 山子研究室.

Two common methods of elimination reactions are dehydrohalogenation of alkyl halides and dehydration of alcohols. A typical example is shown below; note that if possible, the H is anti to the leaving group, even though this leads to the less stable Z-isomer.

For example, the dehydration of ethanol produces ethene: Alkenes can be prepared indirectly from alkyl amines. The amine or ammonia is not a suitable leaving group, so the amine is first either alkylated as in the Hofmann elimination or oxidized to an amine oxide the Cope reaction to render a smooth elimination possible.

Synthesis from carbonyl compounds[ edit ] Another important method for alkene synthesis involves construction of a new carbon—carbon double bond by coupling of a carbonyl compound such as an aldehyde or ketone to a carbanion equivalent.

Such reactions are sometimes called olefinations. The most well-known of these methods is the Wittig reactionbut other related methods are known.

Acyclic diene metathesis mechanism

The Wittig reagent is itself prepared easily from triphenylphosphine and an alkyl halide. The reaction is quite general and many functional groups are tolerated, even esters, as in this example: This uses a less accessible silicon-based reagent in place of the phosphorane, but it allows for the selection of E- or Z-products.

If an E-product is desired, another alternative is the Julia olefinationwhich uses the carbanion generated from a phenyl sulfone. The Takai olefination based on an organochromium intermediate also delivers E-products.

A titanium compound, Tebbe's reagentis useful for the synthesis of methylene compounds; in this case, even esters and amides react. A pair of carbonyl compounds can also be reductively coupled together with reduction to generate an alkene.

Symmetrical alkenes can be prepared from a single aldehyde or ketone coupling with itself, using titanium metal reduction the McMurry reaction.

If two different ketones are to be coupled, a more complex, indirect method such as the Barton—Kellogg reaction may be used.

A single ketone can also be converted to the corresponding alkene via its tosylhydrazone, using sodium methoxide the Bamford—Stevens reaction or an alkyllithium the Shapiro reaction. Olefin metathesis Alkenes can be prepared by exchange with other alkenes, in a reaction known as olefin metathesis.

Frequently, loss of ethene gas is used to drive the reaction towards a desired product. In many cases, a mixture of geometric isomers is obtained, but the reaction tolerates many functional groups.

Alkene - Wikipedia

The method is particularly effective for the preparation of cyclic alkenes, as in this synthesis of muscone: Transition metal catalyzed hydrovinylation is another important alkene synthesis process starting from alkene itself. The hydrovinylation reaction was first reported by Alderson, Jenner, and Lindsey by using rhodium and ruthenium salts, other metal catalysts commonly employed nowadays included iron, cobalt, nickel, and palladium.

The addition can be done highly regio- and stereoselectively, the choices of metal centers, ligands, substrates and counterions often play very important role. If the cis-alkene is desired, hydrogenation in the presence of Lindlar's catalyst a heterogeneous catalyst that consists of palladium deposited on calcium carbonate and treated with various forms of lead is commonly used, though hydroboration followed by hydrolysis provides an alternative approach.

Reduction of the alkyne by sodium metal in liquid ammonia gives the trans-alkene. Rearrangements and related reactions[ edit ] Alkenes can be synthesized from other alkenes via rearrangement reactions. Besides olefin metathesis described abovea large number of pericyclic reactions can be used such as the ene reaction and the Cope rearrangement.

In the Diels—Alder reactiona cyclohexene derivative is prepared from a diene and a reactive or electron-deficient alkene. Nomenclature[ edit ] Although the nomenclature is not followed widely, according to IUPAC, alkenes are acyclic hydrocarbons with one double bond between carbon centers.

Olefins comprise a larger collection of cyclic and acyclic alkenes as well as dienes and polyenes. In higher alkenes, where isomers exist that differ in location of the double bond, the following numbering system is used:Sodium triacetoxyborohydride is presented as a general reducing agent for the reductive amination of aldehydes and ketones.

Procedures for using this mild and selective reagent have been developed for a wide variety of substrates. The scope of the reaction includes aliphatic acyclic and cyclic ketones, aliphatic and aromatic . Olefin: Olefin, compound made up of hydrogen and carbon that contains one or more pairs of carbon atoms linked by a double bond.

Olefins are examples of unsaturated hydrocarbons (compounds that contain only hydrogen and carbon and at least one double or . Sodium triacetoxyborohydride is presented as a general reducing agent for the reductive amination of aldehydes and ketones. Procedures for using this mild and selective reagent have been developed for a wide variety of substrates.

The scope of the reaction includes aliphatic acyclic and cyclic ketones, aliphatic and aromatic aldehydes, and primary and secondary amines including a variety of. Organic Chemistry Animations Welcome to the Introductory Page.

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This site contains interactive 3D animations for some of the most important organic reactions covered during an undergraduate degree. Olefin: Olefin, compound made up of hydrogen and carbon that contains one or more pairs of carbon atoms linked by a double bond.

Olefins are examples of unsaturated hydrocarbons (compounds that contain only hydrogen and carbon and at least one double or . Click the structures and reaction arrows in sequence to view the 3D models and animations respectively.

Acid chlorides can be prepared by reacting a carboxylic acid with thionyl chloride.

Step-growth polymerization - Wikipedia