What is "cyclooctadiene"

n. (context organic compound English) Any of several isomers of a cycloalkene having an eight-membered ring and two double bonds, but especially ''1,5-cyclooctadiene'' that is used as a ligand in organometallic chemistry

A cyclooctadiene (sometimes abbreviated COD) is any of several cyclic diene with the formula (CH)CH. Focusing only on cis derivatives, four isomers are possible: 1,2-, which is an allene, 1,3-, 1,4-, and 1,5-. Commonly encountered isomers are 1,3-cyclooctadiene and 1,5-cyclooctadiene, which is used as a ligand for transition metals. All of these dienes are colorless liquids.