The term "'farnesene "'refers to a set of six closely related chemical compounds which all are sesquiterpenes . ?-Farnesene and ?-farnesene are isomers, differing by the location of one double bond . ?-Farnesene is 3, 7, 11-trimethyl-1, 3, 6, 10-dodecatetraene and ?-farnesene is 7, 11-dimethyl-3-methylene-1, 6, 10-dodecatriene.