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 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.

Preparation and use[edit]

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. Tthe exocyclic double bond (the ethylidene group) undergoes sulfur vulcanization.


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. S2CID 21154862.{{cite journal}}: CS1 maint: uses authors parameter (link)