c9h18o

from The Collaborative International Dictionary of English v.0.48

Nonone \Non"one\, n. [Nonane + -one, suffix denoting the third
   degree of unsaturation.] (Chem.)
   1. Any one of several metameric unsaturated hydrocarbons
      ({C9H14}) of the valylene series. [archaic?]
      [1913 Webster]

   2. Any of several isomeric ketones ({C9H18O}) conceptually
      derived from nonane by substituting an oxygen for two
      hydrogen atoms on one of the non-terminal carbon atoms.
      [PJC]