Chemistry:1,3-Cyclohexadiene
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| Names | |||
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| IUPAC name
Cyclohexa-1,3-diene
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| Other names
1,3-Cyclohexadiene, 1,2-Dihydrobenzene, 1,3-CHD
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| Identifiers | |||
3D model (JSmol)
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PubChem CID
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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 | |||
EU classification (DSD) (outdated)
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Flammable (F) | ||
| R-phrases (outdated) | R11 | ||
| S-phrases (outdated) | S9 S16 S29 S33 | ||
| Flash point | 26 °C (79 °F; 299 K) c.c. | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |||
 verify (what is   ?)
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| Infobox references | |||
1,3-Cyclohexadiene is an organic compound with the formula (CH2)2(CH)4. It is a colorless, flammable liquid. Its refractive index is 1.475 (20 °C, D). A naturally occurring derivative of 1,3-cyclohexadiene is terpinene, a component of pine oil.
Synthesis
Cyclohexadiene is prepared by the dehydrobromination of 1,2-dibromocyclohexane:[1]
- (CH2)4(CHBr)2 + 2 NaH → (CH2)2(CH)4 + 2 NaBr + 2 H2
1,3-Cyclohexadiene can also be prepared by the electrocyclic reaction from 1,3,5-hexatriene either photochemically or at temperatures above 110 °C.[2]
Reactions
Useful reactions of this diene are cycloadditions, such as the Diels-Alder reaction.[3]
Conversion of 1,3-cyclohexadiene to benzene + hydrogen is exothermic by about 25 kJ/mol (gas phase).[4][5]
- cyclohexane → 1,3-cyclohexadiene + 2 H2 ΔH +231.5 kJ/mol (endothermic)
- cyclohexane → benzene + + 3 H2 ΔH +205 kJ (endothermic)
- 1,3-cyclohexadiene → benzene + H2 ΔH -26.5 kJ (exothermic)
Compared with its isomer 1,4-cyclohexadiene, 1,3-cyclohexadiene is about 8.5 kJ/mol more stable.[6]
Cyclohexadiene and its derivatives form metal-alkene 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]+.[7] Cyclohexadienes react with ruthenium trichloride to give (benzene)ruthenium dichloride dimer.
See also
References
- ↑ John P. Schaefer and Leland Endres (1967). "1,3-Cyclohexadiene". Organic Syntheses 47: 31. http://www.orgsyn.org/demo.aspx?prep=CV5P0285.; Collective Volume, 5, pp. 285
- ↑ Roberts, Stanley (1995). Comprehensive Organic Functional Group Transformations: Synthesis: Carbon with No Attached Heteroatoms. Cambridge, UK: Elsevier Science Ltd.. pp. 419. ISBN 0080423221. https://books.google.com/books?id=0ukR60lO5S8C&pg=PA419&lpg=PA419&dq=Synthesis:+Carbon+with+No+Attached+Heteroatoms+1,3-cyclohexadiene&source=bl&ots=LE6rkA-F6O&sig=QNVGDVLg0R8e5rYPLZs672t-Esw&hl=en&sa=X&ei=WAviUND1HMm7iwLDhYGABQ&ved=0CDIQ6AEwAA#v=onepage&q=Synthesis%3A%20Carbon%20with%20No%20Attached%20Heteroatoms%201%2C3-cyclohexadiene&f=false.
- ↑ 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 WebBook 1,3-Cyclohexadiene Benzene
- ↑ J. Sherman The heats of hydrogenation of unsaturated hydrocarbons Journal of the American Oil Chemists' Society; Volume 16, Number 2 / February, 1939
- ↑ NIST Chemistry WebBook 1,4-Cyclohexadiene
- ↑ Pearson, Anthony J.; Sun, Huikai (2008). "Cyclohexadieneiron Tricarbonyl". e-EROS Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rn00791.
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