Cyclohexa-1,3-diene is anorganic compound 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 ofcyclohexadiene, the other being1,4-cyclohexadiene.
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| Names | |||
|---|---|---|---|
| Preferred IUPAC name Cyclohexa-1,3-diene | |||
| Other names 1,3-Cyclohexadiene, 1,2-Dihydrobenzene, 1,3-CHD | |||
| Identifiers | |||
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3D model (JSmol) | |||
| 506024 | |||
| ChEBI | |||
| ChemSpider |
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| ECHA InfoCard | 100.008.878 | ||
| EC Number |
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| 1657 | |||
| RTECS number |
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| UNII | |||
| UN number | 1993 | ||
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| Properties | |||
| C6H8 | |||
| Molar mass | 80.13 g/mol | ||
| Appearance | Colorless liquid | ||
| Density | 0.841 g/cm3 | ||
| Melting point | −98 °C (−144 °F; 175 K) | ||
| Boiling point | 80 °C (176 °F; 353 K) | ||
| −48.6·10−6 cm3/mol | |||
| Hazards | |||
| GHS labelling: | |||
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| Danger | |||
| H225,H335 | |||
| P210,P233,P240,P241,P242,P243,P261,P271,P280,P303+P361+P353,P304+P340,P312,P370+P378,P403+P233,P403+P235,P405,P501 | |||
| Flash point | 26 °C (79 °F; 299 K) c.c. | ||
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
Synthesis
editCyclohexadiene is prepared by the doubledehydrobromination of 1,2-dibromocyclohexane:[1]
- (CH2)4(CHBr)2 + 2 NaH → (CH2)2(CH)4 + 2 NaBr + 2 H2
Reactions
editUseful reactions of this diene arecycloadditions, such as theDiels-Alder reaction.[2]
Conversion of cyclohexa-1,3-diene to benzene + hydrogen is exothermic by about 25 kJ/mol in the gas phase.[3][4]
- cyclohexane → cyclohexa-1,3-diene + 2 H2 (ΔH = +231.5 kJ/mol; endothermic)
- cyclohexane → benzene + 3 H2 (ΔH = +205 kJ/mol; endothermic)
- cyclohexa-1,3-diene → benzene + H2 (ΔH = -26.5 kJ/mol; exothermic)
Compared with itsisomercyclohexa-1,4-diene, cyclohexa-1,3-diene is about 1.6 kJ/mol more stable.[5]
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)3]+.[6] Cyclohexadienes react withruthenium trichloride to give(Benzene)ruthenium dichloride dimer.[7]
Occurrence
editCyclohexa-1,3-diene itself is rare in nature, but the cyclohexa-1,3-diene motif is fairly common.[8] One example ischorismic acid, an intermediate in theshikimic acid pathway. Of the several examples of theterpenoids andterpenes, a prominent example isphellandrene. An unusual derivative iscis-1,2-dihydrocatechol.
Coenzyme A-conjugated to the 2-position of cyclohexadiene-2-carboxylic acid is an intermediate in the biodegradation of aromatic carboxylic acids.[9]
See also
editReferences
edit- ^Schaefer, John P.; Endres, Leland (1967). "1,3-Cyclohexadiene".Organic Syntheses.47: 31.doi:10.15227/orgsyn.047.0031.
- ^Sanjeeva Rao Guppi, George A. O'Doherty, "1,3-Cyclohexadiene" Encyclopedia of Reagents for Organic Synthesis, 2008 John Wiley & Sons.doi:10.1002/047084289X.rn00921
- ^US National Institute of Standards and Technology, NIST Chemistry WebBook1,3-CyclohexadieneBenzene
- ^J. ShermanThe heats of hydrogenation of unsaturated hydrocarbonsArchived 2011-07-14 at theWayback Machine Journal of the American Oil Chemists' Society; Volume 16, Number 2 / February, 1939
- ^NIST Chemistry WebBook1,4-Cyclohexadiene
- ^Pearson, Anthony J.; Sun, Huikai (2008). "Cyclohexadieneiron Tricarbonyl".E-EROS Encyclopedia of Reagents for Organic Synthesis.doi:10.1002/047084289X.rn00791.ISBN 978-0471936237.
- ^Bennett, M. A.; Huang, T. N.; Matheson, T. W.; Smith, A. K. (1982). "16. (η6 -Hexamethylbenzene)Ruthenium Complexes".(η6-Hexamethylbenzene)ruthenium Complexes. Inorganic Syntheses. Vol. 21. pp. 74–78.doi:10.1002/9780470132524.ch16.ISBN 9780470132524.
- ^Gribble, G.W. (1991). "Natural Products Containing a Cyclohexane, Cyclohexene, or Cyclohexadiene Subunit".Second Supplements to the 2nd Edition of Rodd's Chemistry of Carbon Compounds. pp. 375–445.doi:10.1016/B978-044453347-0.50066-5.ISBN 978-0-444-53347-0.
- ^Porter, A. W.; Young, L. Y. (2014). "Benzoyl-CoA, a Universal Biomarker for Anaerobic Degradation of Aromatic Compounds".Advances in Applied Microbiology.88:167–203.doi:10.1016/B978-0-12-800260-5.00005-X.ISBN 978-0-12-800260-5.PMID 24767428.