Ethylidene norbornene

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Ethylidene norbornene
Other names
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).

Ethylidene norbornene (ENB) is an organic compound that consists of an ethylene group attached to norbornene. It is a colorless liquid. The molecule consists of two sites of unsaturation, one of which participates in the copolymerization and the second of which (the ethylidene) undergoes vulcanization. It is a monomer in the production of the commercial polymer EPDM. The compound consists of E- and Z-stereoisomers, but the mixtures are not separated.

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.


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


  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.{{cite journal}}: CS1 maint: uses authors parameter (link)