Germacra-3,9,11-triene, (E,E)-1,5-cyclodecadiene, 1,5-dimethyl-8-(1-methylethenyl)-,(1E,5E,8S)-1,5-cyclodecadiene, 1,5-dimethyl-8-(1-methylethenyl)-,Germacrenes are a class of volatile organic hydrocarbons, specifically, sesquiterpenes. Germacrenes are typically produced in a number of plant species for their antimicrobial and insecticidal properties, though they also play a role as insect pheromones. Two prominent molecules are germacrene A and germacrene D. Germacrenes are a class of volatile organic hydrocarbons, specifically, sesquiterpenes. Germacrenes are typically produced in a number of plant species for their antimicrobial and insecticidal properties, though they also play a role as insect pheromones. Two prominent molecules are germacrene A and germacrene D.