Dicyclopentadiene

Structural formula
endo -dicyclopentadiene (left) and exo -dicyclopentadiene (right)
General
Surname	Dicyclopentadiene
other names	3a, 4,7,7a-tetrahydro-4,7-methanoindene Tricyclo [5.2.1.0 2,6 ] deca-3,8-diene TCD DCPD dimeric cyclopentadiene
Molecular formula	C 10 H 12
Brief description	colorless to yellowish solid with a camphor-like odor
External identifiers / databases
CAS number 77-73-6 EC number 201-052-9 ECHA InfoCard 100,000,958 PubChem 6492 Wikidata Q419053
properties
Molar mass	132.20 g mol −1
Physical state	solid, liquid in technical quality
density	0.98 g cm −3 ( endo form)
Melting point	33 ° C ( endo -form) 19 ° C ( exo -form)
boiling point	169.8 ° C ( endo -form)
Vapor pressure	3 h Pa (20 ° C)
solubility	practically insoluble in water
Refractive index	1.5050 (35 ° C)
safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary danger H and P phrases H: 226-302-330-315-319-335-411 P: 260-273-284-305 + 351 + 338-310
MAK	DFG : 0.5 ml m −3 or 2.7 mg m −3 Switzerland: 0.5 ml m −3 or 3 mg m −3
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C

Commercially available dicyclopentadiene ( IUPAC -Name: tricyclo [5.2.1.0 ^2,6 ] deca-3,8-diene) is a colorless to pale yellow liquid and belongs to the group of the dienes . Very pure dicyclopentadiene is a solid.

It is the dimer of cyclopentadiene from which it is formed by the Diels-Alder reaction . Due to the geometry of the dicyclopentadiene molecule, two stereoisomeric forms are possible: endo - and exo -dicylopentadiene. The Diels-Alder reaction creates a mixture of both forms. The Diels-Alder reaction is also an equilibrium reaction , so isomerically pure, solid dicyclopentadiene gradually converts back into an endo / exo mixture at room temperature and then contains traces of cyclopentadiene and other Diels-Alder adducts .

Extraction

Dicyclopentadiene is formed when the entire C5 fraction of the steam cracking of naphtha is heated (one ton of naphtha contains approx. 14 kg of dicyclopentadiene). The heating takes place at normal pressure and 30 - 100 ° C for 5 - 24 hours. In the next step, the parts of the fraction with a boiling temperature of 28-50 ° C. are distilled off and dicyclopentadiene with a purity of 85-90% is obtained in the lower part of the fraction.

Chemical properties

At 170 ° C., the dicyclopentadiene decomposes rapidly to form cyclopentadiene, which is further promoted by adding a catalyst such as iron powder. This can be prepared preparatively by separating off the monomer by distillation. The flash point of the dimer is 32 ° C, the ignition temperature is 503 ° C. It is insoluble in water. Dicyclopentadiene is stabilized with butylphenol . The substance mixture of the dicyclopentadiene isomers has a very unpleasant odor similar to terpene to camphor.

Physical Properties

The critical temperature of dicyclopentadiene is 386.8 ° C. at a critical pressure of 3.96 MPa and a critical volume of 445 cm ³ / mol.

use

Dicyclopentadiene is used as a raw material for the production of other chemical compounds (e.g. TCD amines and alcohols). Fully hydrogenated dicyclopentadiene can be rearranged to adamantane with aluminum chloride . Tetrahydro-dicyclopentadiene is used as a jet fuel JP-10 .

Safety instructions and risk assessment

From a volume fraction of 0.8 to 6.3 percent in air, it forms explosive mixtures. Dicyclopentadiene is hazardous to water (WGK 2). Dicyclopentadiene is harmful to health, environmentally hazardous and highly flammable.

In 2015, dicyclopentadiene was included in the EU's ongoing action plan ( CoRAP ) in accordance with Regulation (EC) No. 1907/2006 (REACH) as part of substance evaluation . The effects of the substance on human health and the environment are re-evaluated and, if necessary, follow-up measures are initiated. The reasons for the uptake of dicyclopentadiene were concerns about exposure of workers , high (aggregated) tonnage and high risk characterization ratio (RCR), as well as the possible risk of reproductive toxicity . The re-evaluation has been running since 2016 and is carried out by France .

Individual evidence

1. ↑ ^{a b c d e f g h i} Entry on dicyclopentadiene in the GESTIS substance database of the IFA , accessed on February 1, 2016(JavaScript required) .
2. ↑ ^{a b c} Entry on dicyclopentadiene. In: Römpp Online . Georg Thieme Verlag, accessed on March 20, 2014.
3. ↑ Data sheet dicyclopentadiene from Sigma-Aldrich , accessed on May 13, 2017 ( PDF ).
4. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Organic Compounds, pp. 3-162.
5. ↑ Entry on 3a, 4,7,7a-tetrahydro-4,7-methanoindene in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
6. ↑ Swiss Accident Insurance Fund (Suva): Limit values ​​- current MAK and BAT values (search for 77-73-6 or dicyclopentadiene ), accessed on November 2, 2015.
7. ↑ ^{a b} Ullmann's Encyclopedia of Industrial Chemistry - 7th Edition. Weinheim: Wiley-VCH Verlag GmbH, 2011, Chapter: Cyclopentadienes and Cyclopentene.
8. ↑ Community rolling action plan ( CoRAP ) of the European Chemicals Agency (ECHA): 3a, 4,7,7a-tetrahydro-4,7-methanoindene , accessed on March 26, 2019.