Ethylidene norbornene

Ethylidene norbornene (ENB) is an organic compound that consists of an ethylidene (CH3C(H)=) group attached to norbornene. It is a colorless liquid. The molecule consists of two sites of unsaturation. The compound consists of E- and Z-stereoisomers, but the mixtures are typically not separated.

Ethylidene norbornene
Names
Other names
2-ethylidene-5-norbornene
Identifiers
UNII
Properties
C9H12
Molar mass 120.195 g·mol−1
Appearance colorless liquid
Density 0.893 g/mL
Melting point −80 °C (−112 °F; 193 K)
Boiling point 146 °C (295 °F; 419 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Preparation and use

It is prepared by isomerization of vinyl norbornene, which in turn is obtained by the Diels-Alder reaction of butadiene and cyclopentadiene.[1]

Ethylidene norbornene can be produced in two steps from cyclopentadiene.

It is a monomer that used in the production of the commercial polymer EPDM. Only the ring alkene participates in the copolymerization. The exocyclic double bond (the ethylidene group) undergoes sulfur vulcanization.

Safety

Its LD50 (intravenous, rabbit) ranges from 0.09 (male rabbit) to 0.11 ml/kg (female). It is also a neurotoxin.[2]

References
  1. Behr, Arno (2000). "Organometallic Compounds and Homogeneous Catalysis". Ullmann's Encyclopedia of Industrial Chemistry. p. 10. doi:10.1002/14356007.a18_215. ISBN 3527306730.
  2. Ballantyne, Bryan; Myers, Roy C.; Klonne, Dennis R. (1997). "Comparative acute toxicity and primary irritancy of the ethylidene and vinyl isomers of norbornene". Journal of Applied Toxicology. 17 (4): 211–221. doi:10.1002/(SICI)1099-1263(199707)17:4<211::AID-JAT430>3.0.CO;2-X. PMID 9285533. S2CID 21154862.
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