Cyclohexa-1,3-diene is an
organic compound
Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...
with the formula (C
2H
4)(CH)
4. It is a colorless, flammable liquid. Its refractive index is 1.475 (20 °C, D). It is one of two isomers of
cyclohexadiene, the other being
1,4-cyclohexadiene.
Synthesis
Cyclohexadiene is prepared by the double
dehydrobromination of 1,2-dibromocyclohexane:
:(CH
2)
4(CHBr)
2 + 2 NaH → (CH
2)
2(CH)
4 + 2 NaBr + 2 H
2
Reactions
Useful reactions of this diene are
cycloadditions, such as the
Diels-Alder reaction.
Conversion of cyclohexa-1,3-diene to benzene + hydrogen is exothermic by about 25 kJ/mol in the gas phase.
:cyclohexane → cyclohexa-1,3-diene + 2 H
2 (Δ''H'' = +231.5 kJ/mol; endothermic)
:cyclohexane → benzene + 3 H
2 (Δ''H'' = +205 kJ/mol; endothermic)
:cyclohexa-1,3-diene → benzene + H
2 (Δ''H'' = -26.5 kJ/mol; exothermic)
Compared with its
isomer
In chemistry, isomers are molecules or polyatomic ions with identical molecular formula – that is, the same number of atoms of each element (chemistry), element – but distinct arrangements of atoms in space. ''Isomerism'' refers to the exi ...
cyclohexa-1,4-diene, cyclohexa-1,3-diene is about 1.6 kJ/mol more stable.
Cyclohexadiene and its derivatives form
(diene)iron tricarbonyl complexes. Illustrative is
C6H8)Fe(CO)3 an orange liquid. This complex reacts with hydride-abstracting reagents to give the cyclohexadienyl derivative
C6H7)Fe(CO)3sup>+. Cyclohexadienes react with
ruthenium trichloride to give
(Benzene)ruthenium dichloride dimer.
Occurrence
Cyclohexa-1,3-diene itself is rare in nature, but the cyclohexa-1,3-diene motif is fairly common.
One example is
chorismic acid
Chorismic acid, more commonly known as its ion, anionic form chorismate, is an important biochemical intermediate in plants and microorganisms. It is a precursor for:
* The aromatic amino acids phenylalanine, tryptophan, and tyrosine
* Indole, ind ...
, an intermediate in the
shikimic acid pathway. Of the several examples of the
terpenoid
The terpenoids, also known as isoprenoids, are a class of naturally occurring organic compound, organic chemicals derived from the 5-carbon compound isoprene and its derivatives called terpenes, diterpenes, etc. While sometimes used interchangeabl ...
s and
terpene
Terpenes () are a class of natural products consisting of compounds with the formula (C5H8)n for n ≥ 2. Terpenes are major biosynthetic building blocks. Comprising more than 30,000 compounds, these unsaturated hydrocarbons are produced predomi ...
s, a prominent example is
phellandrene
Phellandrenes are organic compounds with the formula . They have a similar molecular structure and similar chemical properties. α-Phellandrene and β-phellandrene are cyclic monoterpenes and are double-bond isomers. In α-phellandrene, both dou ...
. An unusual derivative is
''cis''-1,2-dihydrocatechol.
Coenzyme A
Coenzyme A (CoA, SHCoA, CoASH) is a coenzyme, notable for its role in the Fatty acid metabolism#Synthesis, synthesis and Fatty acid metabolism#.CE.B2-Oxidation, oxidation of fatty acids, and the oxidation of pyruvic acid, pyruvate in the citric ac ...
-conjugated to the 2-position of cyclohexadiene-2-carboxylic acid is an intermediate in the biodegradation of aromatic carboxylic acids.
See also
*
1,4-Cyclohexadiene
*
Cyclohexene
Cyclohexene is a hydrocarbon with the formula . It is a cycloalkene. At room temperature, cyclohexene is a colorless liquid with a sharp odor. Among its uses, it is an chemical intermediate, intermediate in the commercial synthesis of nylon.
Prod ...
References
{{DEFAULTSORT:Cyclohexadiene, 1, 3-
Cyclohexadienes
Conjugated dienes