tetrinic

from The Century Dictionary.

• Pertaining to a compound with four carbon atoms.

from the GNU version of the Collaborative International Dictionary of English.

• adjective (Chem.) Of, pertaining to, or designating, a complex ketonic acid, C5H6O3, obtained as a white crystalline substance; -- so called because once supposed to contain a peculiar radical of four carbon atoms. Called also acetyl-acrylic acid.