C10H21.CO2H

from The Collaborative International Dictionary of English v.0.48
Undecylic \Un`de*cyl"ic\, a. (Chem.)
   Related to, derived from, or containing, the undecyl radical;
   specifically, designating that member of the fatty acids
   which corresponds to undecane, and is obtained as a white
   crystalline substance, {C10H21.CO2H}.
   [1913 Webster]
    

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