eucalyptol

from The Collaborative International Dictionary of English v.0.48
eucalyptol \eu`ca*lyp*tol\, n. [eucalyptus + L. oleum oil.]
   (Chem.)
   A volatile, terpenelike oil ({C10H18O}), which is the main
   constituent of the oil of eucalyptus. It has cockroach
   repellent activity and is used as a flavoring aid in
   pharmaceuticals. Chemically it is
   1,3,3-trimethyl-2-oxabicyclo-[2,2,2]-octane. --MI11

   Syn: cineole, cajeputol. [1913 Webster +PJC]

   Note: In the 1913 Webster eucalytpol was defined as an oil
         "consisting largely of cymene". Cymene
         (isopropyltoluene, {C10H14}) differs from that of the
         substance currently called eucalyptol, in having an
         unsaturated ring and no oxygen. Para-cymene does occur
         in eucalyptus oil as well as some other essential oils.
         [PJC]