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 (C₂H₄)(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 Cyclohexadiene may refer to: * Cyclohexa-1,3-diene, * Cyclohexa-1,4-diene, See also

* Benzene or its theoretical isomer ''1,3,5-Cyclohexatriene'' * Cyclohexene {{chemistry index ...

, the other being

1,4-cyclohexadiene 1,4-Cyclohexadiene is an organic compound with the formula C6H8. It is a colourless, flammable liquid that is of academic interest as a prototype of a large class of related compounds called terpenoids, an example being γ-terpinene. An isomer of ...

Synthesis

Cyclohexadiene is prepared by the double dehydrobromination of 1,2-dibromocyclohexane: :(CH₂)₄(CHBr)₂ + 2 NaH → (CH₂)₂(CH)₄ + 2 NaBr + 2 H₂

Reactions

Useful reactions of this diene are

cycloaddition In organic chemistry, a cycloaddition is a chemical reaction in which "two or more Unsaturated hydrocarbon, unsaturated molecules (or parts of the same molecule) combine with the formation of a cyclic adduct in which there is a net reduction of th ...

s, 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 H₂ (Δ''H'' = +231.5 kJ/mol; endothermic) :cyclohexane → benzene + 3 H₂ (Δ''H'' = +205 kJ/mol; endothermic) :cyclohexa-1,3-diene → benzene + H₂ (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 1,4-Cyclohexadiene is an organic compound with the formula C6H8. It is a colourless, flammable liquid that is of academic interest as a prototype of a large class of related compounds called terpenoids, an example being γ-terpinene. An isomer of ...

, 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 Ruthenium(III) chloride is the chemical compound with the formula RuCl3. "Ruthenium(III) chloride" more commonly refers to the hydrate RuCl3·''x''H2O. Both the anhydrous and hydrated species are dark brown or black solids. The hydrate, with a var ...

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.

References

{{DEFAULTSORT:Cyclohexadiene, 1, 3- Cyclohexadienes Conjugated dienes