The Collaborative International Dictionary of English v.0.48:

Terpenylic \Ter`pe*nyl"ic\, a. [Terpene + -yl + -ic.] (Chem.)
   Of, pertaining to, or designating, an acid, C8H12O4 (called
   also terpentic acid), homologous with terebic acid, and
   obtained as a white crystalline substance by the oxidation of
   oil of turpentine with chromic acid.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Xeronic \Xe*ron"ic\, a. [Gr. xhro`s dry + citraconic.] (Chem.)
   Pertaining to, or designating, an acid, C8H12O4, related to
   fumaric acid, and obtained from citraconic acid as an oily
   substance having a bittersweet taste; -- so called from its
   tendency to form its anhydride.
   [1913 Webster]