1,3-Cyclohexadiene
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| Names | |||
|---|---|---|---|
| IUPAC name
Cyclohexa-1,3-diene | |||
| Other names
1,3-Cyclohexadiene, 1,2-Dihydrobenzene, 1,3-CHD | |||
| Identifiers | |||
592-57-4  | |||
| 3D model (Jmol) | Interactive image | ||
| ChEBI | CHEBI:37610 | ||
| ChemSpider | 11117 | ||
| ECHA InfoCard | 100.008.878 | ||
| PubChem | 11605 | ||
| RTECS number | GU4702350 | ||
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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) | ||
| Hazards | |||
| EU classification (DSD) |
Flammable (F) | ||
| R-phrases | R11 | ||
| S-phrases | 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). | |||
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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
1,3-Cyclohexadiene can be used as a hydrogen donor in transfer hydrogenation, since its conversion to benzene + hydrogen is exothermic by about 25 kJ/mol (gas phase). [3][4]
- 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.[5]
See also
References
- ↑ John P. Schaefer and Leland Endres (1967). "1,3-Cyclohexadiene". Org. Synth. 47: 31.; Coll. Vol., 5, p. 285
- ↑ Roberts, Stanley (1995). Comprehensive Organic Functional Group Transformations: Synthesis: Carbon with No Attached Heteroatoms. Cambridge, UK: Elsevier Science Ltd. p. 419. ISBN 0080423221.
- ↑ 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