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Diene

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Title: Diene  
Author: World Heritage Encyclopedia
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Subject: Inverse electron-demand Diels–Alder reaction, Alkene, Ethylene propylene rubber, Pregnadiene, Hydroamination
Collection: Dienes
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Diene

In

  1. ^ Roger Bishop, "9-Thiabicyclo[3.3.1]nonane-2,6-dione",  
  2. ^ RyoShintani, Tamio Hayashi, "Chiral Diene Ligands for Asymmetric Catalysis" Aldrich Chimica Acta 2009, vol. 42, number 2, pp. 31-38.

References

External links

See also

Dienes are widely used chelating bis(cyclooctadiene)nickel(0) are labile. In some cases, dienes are spectator ligands, remaining coordinated throughout a catalytic cycle and influencing the product distributions. Chiral dienes have also been described.[2]

As ligands

Conjugated and 1,4-dienes generally are somewhat acidic since deprotonation of both classes gives pentadienyl anions. The acidifying effect of the diene is very pronounced in cyclopentadiene.

Acidity

Nonconjugated dienes are substrates for ring-closing metathesis reactions. These reactions require a metal catalyst:

Metathesis reactions

2,6-Dichloro-9-thiabicyclo[3.3.1]nonane, synthesis and reactions

Conjugated dienes add reagents such as bromine and hydrogen by both 1,2-addition and 1,4-addition pathways. Addition of polar reagents can generate complex architectures:[1]

Other addition reactions

An important reaction for conjugated dienes is the Diels–Alder reaction. Many specialized dienes have been developed to exploit this reactivity for the synthesis of natural products (e.g., Danishefsky's diene).

Cycloadditions

The most heavily practiced reaction of alkenes, dienes included, is polymerization. 1,3-Butadiene is a precursor to rubber used in tires, and isoprene is the precursor to natural rubber. Chloroprene is related but it is a synthetic monomer.

Polymerization

Reactivity and uses

Diene-containing fatty acids are biosynthesized from acetyl CoA.

In the laboratory, more directed and more delicate processes are employed such as methods have been developed, such as the Whiting reaction. Families of nonconjugated dienes are derived from the oligomerization and dimerization of conjugated dienes. For example, 1,5-cyclooctadiene and vinylcyclohexene are produced by dimerization of 1,3-butadiene.

On an industrial scale, butadiene is prepared by thermal cracking of butanes. In a similarly non-selective process, dicyclopentadiene is obtained from coal tars.

Synthesis of dienes

Some dienes: A: 1,2-Propadiene, also known as allene, is the simplest cumulated diene. B: Isoprene, also known as 2-methyl-1,3-butadiene, the precursor to natural rubber. C: 1,3-Butadiene, a precursor to synthetic polymers. D: 1,5-Cyclooctadiene, an unconjugated diene (notice that each double bond is two carbons away from the other). E: Norbornadiene, a strained bicyclic and unconjugated diene. F: Dicyclopentadiene. G: Linoleic acid, a fatty acid that is required in the human diet.

Compounds that contain more than two double bonds are called polyenes. Polyenes and dienes share many of their properties.

  1. Cumulated dienes have the double bonds sharing a common atom as in a group of compounds called allenes.
  2. Conjugated dienes have conjugated double bonds separated by one single bond.
  3. Unconjugated dienes have the double bonds separated by two or more single bonds. They are usually less stable than isomeric conjugated dienes. This can also be known as an isolated diene.

Dienes can be divided into three classes, depending on the relative location of the double bonds:

Classes

Contents

  • Classes 1
  • Synthesis of dienes 2
  • Reactivity and uses 3
    • Polymerization 3.1
    • Cycloadditions 3.2
    • Other addition reactions 3.3
    • Metathesis reactions 3.4
    • Acidity 3.5
    • As ligands 3.6
  • See also 4
  • External links 5
  • References 6

industry. polymer in the monomers dienes are widely used as Conjugated. Dienes occur occasionally in nature. double bonds carbon that contains two hydrocarbon) is a (diolefin) or

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