1,5-Cyclooctadiene | |
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Cycloocta-1,5-diene[1] |
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Identifiers | |
Abbreviations | 1,5-COD |
CAS number | 111-78-4 , 1552-12-1 (1Z,5Z)-1,5-diene, 5259-71-2 (1Z,5E)-1,5-diene, 17612-50-9 (1E,5E)-1,5-diene |
PubChem | 8135, 10937607 (5Z)-5-ene, 82916 (1Z,5Z)-1,5-diene, 5364364 (1Z,5E)-1,5-diene, 5702534 (1E,5E)-1,5-diene |
ChemSpider | 7843 , 74815 (1Z,5Z)-1,5-diene , 18520443 (1Z,5E)-1,5-diene , 19971660 (1E,5E)-1,5-diene |
EC number | 203-907-1 |
UN number | 2520 |
MeSH | 1,5-cyclooctadiene |
RTECS number | GX9560000 GX9620000 (1Z,5Z)-1,5-diene |
Beilstein Reference | 2036542 1209288 (1Z,5Z)-1,5-diene |
Jmol-3D images | Image 1 |
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Properties | |
Molecular formula | C8H12 |
Molar mass | 108.18 g mol−1 |
Exact mass | 108.093900384 g mol-1 |
Appearance | Colorless liquid |
Density | 882 mg cm-3 |
Melting point |
-69 °C, 204 K, -92 °F |
Boiling point |
150 °C, 423 K, 302 °F |
Vapor pressure | 910 Pa |
Refractive index (nD) | 1.493 |
Thermochemistry | |
Std enthalpy of formation ΔfH |
21-27 kJ mol-1 |
Std enthalpy of combustion ΔcH |
-4.890--4.884 MJ mol-1 |
Standard molar entropy S |
250.0 J K-1 mol-1 |
Specific heat capacity, C | 198.9 J K-1 mol-1 |
Hazards | |
GHS pictograms | |
GHS signal word | DANGER |
GHS hazard statements | H226, H304, H315, H317, H319, H334 |
GHS precautionary statements | P261, P280, P301+310, P305+351+338, P331, P342+311 |
EU classification | Xn |
R-phrases | R10, R36/38, R42/43, R65 |
S-phrases | S23, S26, S36/37, S62 |
Flash point | 32–38 °C |
Autoignition temperature |
222 °C |
(verify) (what is: / ?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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Infobox references |
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.[2][3]
Contents |
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.[4]
COD reacts with borane to give 9-borabicyclo[3.3.1]nonane,[5] commonly known as 9-BBN, a reagent in organic chemistry used in hydroborations:
COD adds SCl2 (or similar reagents) to give 2,6-dichloro-9-thiabicyclo[3.3.1]nonane:[6]
The resulting dichloride can be further modified as the di-azide or di-cyano derivative in a nucleophilic substitution aided by anchimeric assistance.
1,5-COD typically binds to low-valence metals via both alkene groups. The complex Ni(cod)2 is a precursor to several nickel(0) and Ni(II) complexes. 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.
Ni(COD)2 is prepared by reduction of anhydrous nickel acetylacetonate in the presence of the ligand, using triethylaluminium [7]
The related Pt(COD)2 is prepared by a more circuitous route involving the dilithium cyclooctatetraene:[8]
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 has been used in many syntheses:
COD complexes are useful as starting materials, one noteworthy example is the reaction:
The product Ni(CO)4 is highly toxic, thus it is advantageous to generate it in the reaction vessel as opposed to being dispensed directly. Other low-valent metal complexes of COD include Mo(COD)(CO)4, [RuCl2(COD)]n, and Fe(COD)(CO)3. COD is an especially important in the coordination chemistry of rhodium(I) and iridium(I), examples being Crabtree's catalyst and cyclooctadiene rhodium chloride dimer. The square planar complexes [M(COD)2]+ are known (M = Rh, Ir).
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.[9] Another synthesis (double elimination reaction from a cyclooctane ring) was reported by Huisgen in 1987.[10] The molecular conformation of (E,E)-COD is twisted rather than chair-like. The compound has been investigated as a click chemistry mediator.[11]
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