The Collaborative International Dictionary of English v.0.48:

Pentadecylic \Pen`ta*decyl"ic\
   (p[e^]n`t[.a]*d[-e]*s[i^]l"[i^]k), a. [Penta- + decylic.]
   (Chem.)
   Same as Quindecylic.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Quindecylic \Quin`de*cyl"ic\, n. [L. quindecim fifteen + -yl.]
   (Chem.)
   Pertaining to, or designating, an acid of the fatty acid
   series, containing fifteen atoms of carbon; called also
   pentadecylic acid.
   [1913 Webster]