|Systematic IUPAC name
|Molar mass||108.18 g·mol−1|
|Melting point||−69 °C; −92 °F; 204 K|
|Boiling point||150 °C; 302 °F; 423 K|
|Vapor pressure||910 Pa|
Refractive index (nD)
|198.9 J K−1 mol−1|
|250.0 J K−1 mol−1|
Std enthalpy of
|21-27 kJ mol−1|
Std enthalpy of
|-4.890--4.884 MJ mol−1|
|GHS signal word||DANGER|
|H226, H304, H315, H317, H319, H334|
|P261, P280, P301+310, P305+351+338, P331, P342+311|
|R-phrases||R10, R36/38, R42/43, R65|
|S-phrases||S23, S26, S36/37, S62|
|Flash point||32 to 38 °C (90 to 100 °F; 305 to 311 K)|
|222 °C (432 °F; 495 K)|
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
|what is: / ?)(|
1,5-Cyclooctadiene is the organic compound with the chemical formula C8H12. Generally abbreviated COD, this diene is a useful precursor to other organic compounds and serves as a ligand in organometallic chemistry. It is a colorless liquid with a strong odor. 1,5-Cyclooctadiene can be prepared by dimerization of butadiene in the presence of a nickel catalyst, a coproduct being vinylcyclohexene. Approximately 10,000 tons were produced in 2005.
COD adds SCl2 (or similar reagents) to give 2,6-dichloro-9-thiabicyclo[3.3.1]nonane:
1,5-COD binds to low-valent metals via both alkene groups. Metal-COD complexes are attractive because they are sufficiently stable to be isolated, often being more robust than related ethylene complexes. The stability of COD complexes is attributable to the chelate effect. The COD ligands are easily displaced by other ligands, such as phosphines.
- 1/3 [Ni(C5H7O2)2]3 + 2 COD + 2 Al(C2H5)3 → Ni(COD)2 + 2 Al(C2H5)2(C5H7O2) + C2H4 + C2H6
- Li2C8H8 + PtCl2(COD) + 3 C7H10 → [Pt(C7H10)3] + 2 LiCl + C8H8 + C8H12
- Pt(C7H10)3 + 2 COD → Pt(COD)2 + 3 C7H10
Extensive work has been reported on complexes of COD, much of which can has been described in volumes 25, 26, and 28 of Inorganic Syntheses. The platinum complex is a precursor to an 16e complex of ethylene:
- Pt(COD)2 + 3 C2H4 → Pt(C2H4)3 + 2 COD
COD complexes are useful as starting materials, one noteworthy example is the reaction:
- Ni(COD)2 + 4 CO → Ni(CO)4 + 2 COD
The product Ni(CO)4 is highly toxic, thus it is advantageous to generate it in the reaction vessel upon demand. Other low-valent metal complexes of COD include cyclooctadiene rhodium chloride dimer, cyclooctadiene iridium chloride dimer, and Fe(COD)(CO)3, and Crabtree's catalyst.
The highly strained trans-trans isomer of 1,5-cyclooctadiene is a known compound. (E,E)-COD was first synthesized by Whitesides and Cope in 1969 by photoisomerization of the cis compound. Another synthesis (double elimination reaction from a cyclooctane ring) was reported by Huisgen in 1987. The molecular conformation of (E,E)-COD is twisted rather than chair-like. The compound has been investigated as a click chemistry mediator.
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