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Cyclopentadiene

 

 
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Cyclopentadiene
 
 
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Cyclopentadiene is a chemical compound
Chemical compound

A chemical compound is a Chemical substance consisting of two or more different chemical element Chemical bond together in a fixed mass ratio that can be split into simpler substances....
 with the formula
Chemical formula

A chemical formula is a way of expressing information about the atoms that constitute a particular chemical compound, and how the relationship between those atoms changes in chemical reactions....
 C5H6. This colorless liquid organic
Organic chemistry

Organic chemistry is a discipline within chemistry which involves the science study of the structure, properties, composition, chemical reaction, and preparation of chemical compounds that contain carbon....
 chemical
Chemical compound

A chemical compound is a Chemical substance consisting of two or more different chemical element Chemical bond together in a fixed mass ratio that can be split into simpler substances....
 has a strong and unpleasant odor. At room temperature, this cyclic diene
Diene

Dienes or diolefins are hydrocarbons which contain two covalent bond. Dienes are intermediate between alkenes and polyenes....
 dimer
Dimer

File:Carboxylic acid dimers.pngA dimer is a chemical or biological entity consisting of two identical subunits called monomers, which are held together by either intramolecular forces or weaker intermolecular forces....
izes over the course of hours to give dicyclopentadiene
Dicyclopentadiene

Dicyclopentadiene, abbreviated DCPD, is the chemical compound with the formula C10H12. At room temperature, it is a white crystalline solid with a camphor-like odor....
 via a Diels-Alder reaction
Diels-Alder reaction

The Diels-Alder reaction is an organic chemical reaction between a conjugated diene and a substituted alkene, commonly termed the dienophile, to form a substituted cyclohexene system....
. This dimer "cracks" to give the monomer upon heating.

The compound is the precursor to the popular cyclopentadienyl-ligand
Ligand

In chemistry, a ligand is either an atom, ion, or molecule that bonds to a central metal, generally involving formal donation of one or more of its electrons....
 ('Cp') in cyclopentadienyl complex
Cyclopentadienyl complex

A cyclopentadienyl complex is a metal complex with one or more cyclopentadienyl groups . Based on the type of bonding between the metals and the cyclopentadiene moieties, cyclopentadienyl complexes are classified into the following three categories: a) p-complexes, b) s-complexes, and c) ionic complexes....
es in organometallic chemistry
Organometallic chemistry

Organometallic chemistry is the study of chemical compounds containing chemical bonding between carbon and a metal. Since many compounds without such bonds are chemically similar, an alternative may be compounds containing metal-element bonds of a largely covalent character....
. Both cyclopentadiene and dicyclopentadiene can serve as ligands as well, but these are uncommon.

hydrogen atoms in cyclopentadiene undergo rapid [1,5]-sigmatropic shifts
Sigmatropic reaction

A Sigmatropic reaction in organic chemistry is a pericyclic reaction wherein the net result is one sigma bond changed to another sigma bond. In this type of rearrangement reaction, a substituent moves from one part of a pi-bonded system to another part in an intramolecular reaction with simultaneous rearrangement of the pi system....
 as indicated by the variable temperature1H NMR spectra
Nuclear magnetic resonance

Nuclear magnetic resonance is the name given to a physical resonance phenomenon involving the observation of specific quantum mechanics magnetism properties of an atomic atomic nucleus in the presence of an applied, external magnetic field....
 recorded at various temperatures.

opentadiene readily undergoes Diels-Alder reaction
Diels-Alder reaction

The Diels-Alder reaction is an organic chemical reaction between a conjugated diene and a substituted alkene, commonly termed the dienophile, to form a substituted cyclohexene system....
s with dienophiles, such as 1,4-benzoquinone
1,4-Benzoquinone

1,4-Benzoquinone is the chemical compound with the chemical formula C6H4O2. In pure state, it forms bright yellow crystals with characteristic irritating odor, resembling that of chlorine; impure samples are often dark colored due to the presence of quinhydrone ....
.

The compound is acid
Acid

An acid is traditionally considered any chemical compound that, when dissolved in water, gives a solution with a hydrogen ion Activity greater than in pure water, i.e....
ic with pKa=16, which is unusual for a hydrocarbon
Hydrocarbon

In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. With relation to chemical terminology, aromatic hydrocarbons or arenes, alkanes, alkenes and alkyne-based compounds composed entirely of carbon or hydrogen are referred to as "pure" hydrocarbons, whereas other hydrocarbons with bonded com...
.






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Encyclopedia


Cyclopentadiene is a chemical compound
Chemical compound

A chemical compound is a Chemical substance consisting of two or more different chemical element Chemical bond together in a fixed mass ratio that can be split into simpler substances....
 with the formula
Chemical formula

A chemical formula is a way of expressing information about the atoms that constitute a particular chemical compound, and how the relationship between those atoms changes in chemical reactions....
 C5H6. This colorless liquid organic
Organic chemistry

Organic chemistry is a discipline within chemistry which involves the science study of the structure, properties, composition, chemical reaction, and preparation of chemical compounds that contain carbon....
 chemical
Chemical compound

A chemical compound is a Chemical substance consisting of two or more different chemical element Chemical bond together in a fixed mass ratio that can be split into simpler substances....
 has a strong and unpleasant odor. At room temperature, this cyclic diene
Diene

Dienes or diolefins are hydrocarbons which contain two covalent bond. Dienes are intermediate between alkenes and polyenes....
 dimer
Dimer

File:Carboxylic acid dimers.pngA dimer is a chemical or biological entity consisting of two identical subunits called monomers, which are held together by either intramolecular forces or weaker intermolecular forces....
izes over the course of hours to give dicyclopentadiene
Dicyclopentadiene

Dicyclopentadiene, abbreviated DCPD, is the chemical compound with the formula C10H12. At room temperature, it is a white crystalline solid with a camphor-like odor....
 via a Diels-Alder reaction
Diels-Alder reaction

The Diels-Alder reaction is an organic chemical reaction between a conjugated diene and a substituted alkene, commonly termed the dienophile, to form a substituted cyclohexene system....
. This dimer "cracks" to give the monomer upon heating.

The compound is the precursor to the popular cyclopentadienyl-ligand
Ligand

In chemistry, a ligand is either an atom, ion, or molecule that bonds to a central metal, generally involving formal donation of one or more of its electrons....
 ('Cp') in cyclopentadienyl complex
Cyclopentadienyl complex

A cyclopentadienyl complex is a metal complex with one or more cyclopentadienyl groups . Based on the type of bonding between the metals and the cyclopentadiene moieties, cyclopentadienyl complexes are classified into the following three categories: a) p-complexes, b) s-complexes, and c) ionic complexes....
es in organometallic chemistry
Organometallic chemistry

Organometallic chemistry is the study of chemical compounds containing chemical bonding between carbon and a metal. Since many compounds without such bonds are chemically similar, an alternative may be compounds containing metal-element bonds of a largely covalent character....
. Both cyclopentadiene and dicyclopentadiene can serve as ligands as well, but these are uncommon.

Properties

The hydrogen atoms in cyclopentadiene undergo rapid [1,5]-sigmatropic shifts
Sigmatropic reaction

A Sigmatropic reaction in organic chemistry is a pericyclic reaction wherein the net result is one sigma bond changed to another sigma bond. In this type of rearrangement reaction, a substituent moves from one part of a pi-bonded system to another part in an intramolecular reaction with simultaneous rearrangement of the pi system....
 as indicated by the variable temperature1H NMR spectra
Nuclear magnetic resonance

Nuclear magnetic resonance is the name given to a physical resonance phenomenon involving the observation of specific quantum mechanics magnetism properties of an atomic atomic nucleus in the presence of an applied, external magnetic field....
 recorded at various temperatures.

Reactivity of cyclopentadiene

Cyclopentadiene readily undergoes Diels-Alder reaction
Diels-Alder reaction

The Diels-Alder reaction is an organic chemical reaction between a conjugated diene and a substituted alkene, commonly termed the dienophile, to form a substituted cyclohexene system....
s with dienophiles, such as 1,4-benzoquinone
1,4-Benzoquinone

1,4-Benzoquinone is the chemical compound with the chemical formula C6H4O2. In pure state, it forms bright yellow crystals with characteristic irritating odor, resembling that of chlorine; impure samples are often dark colored due to the presence of quinhydrone ....
.

The compound is acid
Acid

An acid is traditionally considered any chemical compound that, when dissolved in water, gives a solution with a hydrogen ion Activity greater than in pure water, i.e....
ic with pKa=16, which is unusual for a hydrocarbon
Hydrocarbon

In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. With relation to chemical terminology, aromatic hydrocarbons or arenes, alkanes, alkenes and alkyne-based compounds composed entirely of carbon or hydrogen are referred to as "pure" hydrocarbons, whereas other hydrocarbons with bonded com...
. This relatively high acidity is explained by the stability of the aromatic, anionic
Anionic

In chemistry, an anionic species is one that contains a full electric charge. These types of chemical compound can range in reactivity, but most are fairly reactive.Anionic is a chemical that is also used in things like washing detergent.......
, 5-membered ring (cyclopentadienyl anion, C
Carbon

Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....
5H
Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....
5-). Derivatives of this anion are often depicted as salts, although the free anion does not exist in any appreciable extent in solution. Deprotonation
Deprotonation

Deprotonation is a chemistry term that refers to the removal of a proton from a molecule, forming the conjugate base. The relative ability for a molecule to give up a proton is measured by a pKa value....
 can be achieved, e.g. by alkali metal bases. Sodium cyclopentadienide
Sodium cyclopentadienide

Sodium cyclopentadienide is an organosodium compound. Its chemical formula is C5H5Na, but is often abbreviated to NaCp or CpNa, where Cp− is the Cyclopentadiene....
 is commercially available. The anion serves as a weak nucleophile in organic synthesis
Organic synthesis

Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic_chemistry molecules can often contain a higher level of complexity compared to purely Inorganic_chemistry compounds, so the synthesis of organic compounds has developed into one of the most im...
 and combines with numerous anhydrous halides of the transition metal
Transition metal

In chemistry, the term transition metal has two possible meanings:*It commonly refers to any element in the d-block of the periodic table, including the group 12 element elements zinc, cadmium and Mercury ....
s to form cyclopentadienyl complex
Cyclopentadienyl complex

A cyclopentadienyl complex is a metal complex with one or more cyclopentadienyl groups . Based on the type of bonding between the metals and the cyclopentadiene moieties, cyclopentadienyl complexes are classified into the following three categories: a) p-complexes, b) s-complexes, and c) ionic complexes....
es, such as metallocene
Metallocene

A metallocene is a compound with the general formula 2M consisting of two cyclopentadiene anions bound to a metal center in the oxidation state II....
s.

Uses

Aside from its use as a synthetic intermediate, cyclopentadiene itself has few applications because it reverts so readily to dicyclopentadiene. Cyclopentadiene reacts with linseed oil
Linseed oil

Linseed oil, also known as flax seed oil or simply flax oil, is a clear to yellowish drying oil derived from the dried ripe seeds of the flax plant ....
 to facilitate "drying" upon contact with oxygen.

See also

  • Aromaticity
    Aromaticity

    Aromaticity is a chemical property in which a conjugated system ring of unsaturated bonds, lone pairs, or empty orbitals exhibit a stabilization stronger than would be expected by the stabilization of conjugation alone....
  • Methylcyclopentadiene
    Methylcyclopentadiene

    Methylcyclopentadiene describes three isomeric cyclic diolefins with the formula C5MeH5 . These isomers are the organic precursor to the methylcyclopentadienyl-ligand , commonly found in organometallic chemistry....
     and pentamethylcyclopentadiene
    Pentamethylcyclopentadiene

    1,2,3,4,5-Pentamethylcyclopentadiene is a cyclic olefin with the formula C5Me5H . 1,2,3,4,5-Pentamethylcyclopentadiene is the precursor to the ligand 1,2,3,4,5-pentamethylcyclopentadienyl, which is often denoted as Cp* ....
    , also found as ligands in organometallic chemistry


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