C4H9CO2H

from The Collaborative International Dictionary of English v.0.48
Valeric \Va*ler"ic\, a. (Chem.)
   Valerianic; specifically, designating any one of three
   metameric acids, of which the typical one (called also
   {inactive valeric acid}), {C4H9CO2H}, is obtained from
   valerian root and other sources, as a corrosive, mobile, oily
   liquid, having a strong acid taste, and an odor of old
   cheese.
   [1913 Webster]

   {Active valeric acid}, a metameric variety which turns the
      plane of polarization to the right, although formed by the
      oxidation of a levorotatory amyl alcohol.
      [1913 Webster]
    

[email protected]