Cyclohexa-1,3-diene

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Cyclohexa-1,3-diene
Names
IUPAC name
Cyclohexa-1,3-diene
Other names
1,3-Cyclohexadiene, 1,2-Dihydrobenzene, 1,3-CHD
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.008.878 Edit this at Wikidata
RTECS number
  • GU4702350
  • InChI=1S/C6H8/c1-2-4-6-5-3-1/h1-4H,5-6H2 checkY
    Key: MGNZXYYWBUKAII-UHFFFAOYSA-N checkY
  • InChI=1/C6H8/c1-2-4-6-5-3-1/h1-4H,5-6H2
    Key: MGNZXYYWBUKAII-UHFFFAOYAH
  • C\1=C\C=C/CC/1
Properties
C6H8
Molar mass 80.13 g/mol
Appearance Colourless liquid
Density 0.841 g/cm³
Melting point −98 °C (−144 °F; 175 K)
Boiling point 80 °C (176 °F; 353 K)
Hazards
Flash point c.c. 26 °C (79 °F; 299 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

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 20 kJ/mol (gas phase. [3][4]

cyclohexane → 1,3-cyclohexadiene + 2 H2 ΔH +224 kJ/mol (endothermic)
cyclohexane → benzene + + 3 H2 ΔH +205 kJ (endothermic)
1,3-cyclohexadiene → benzene + H2 ΔH -19 kJ</ref> (exothermic)

Compared with its isomer, 1,4-cyclohexadiene, 1,3-cyclohexadiene is about 1.6 kJ/mol less stable.[5]

See also

References

  1. ^ John P. Schaefer and Leland Endres (1967). "1,3-Cyclohexadiene". Organic Syntheses. 47: 31; Collected Volumes, vol. 5, p. 285.
  2. ^ Roberts, Stanley (1995). Comprehensive Organic Functional Group Transformations: Synthesis: Carbon with No Attached Heteroatoms. Cambridge, UK: Elsevier Science Ltd. p. 419. ISBN 0080423221.
  3. ^ US National Institute of Standards and Technology, NIST Chemistry WebBook 1,3-Cyclohexadiene Benzene
  4. ^ J. Sherman The heats of hydrogenation of unsaturated hydrocarbons Journal of the American Oil Chemists' Society; Volume 16, Number 2 / February, 1939
  5. ^ NIST Chemistry WebBook 1,4-Cyclohexadiene
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