Isoprene /(?)/

I·so·prene

Isoprene

n.
  1. An oily, volatile unsaturated hydrocarbon (C5H8), obtained by the distillation of caoutchouc or gutta-percha, and used to make synthetic rubber by polymerization. In organic chemistry, it is viewed conceptually as the building block of the terpene series of hydrocarbons. (Chem.)