C5H11NO2

from The Collaborative International Dictionary of English v.0.48

Amyl nitrite \Amyl nitrite\
   A yellowish oily volatile liquid, {C5H11NO2}, used in
   medicine as a heart stimulant and a vasodilator. The
   inhalation of its vapor instantly produces flushing of the
   face.
   [Webster 1913 Suppl.]

from The Collaborative International Dictionary of English v.0.48

Betaine \Be"ta*ine\, n. [From beta, generic name of the beet.]
   (Chem.)
   A nitrogenous base, {C5H11NO2}, produced artificially, and
   also occurring naturally in beet-root molasses and its
   residues, from which it is extracted as a white crystalline
   substance; -- called also {lycine} and {oxyneurine}. It has a
   sweetish taste.
   [1913 Webster]