chloranil

from The Century Dictionary.

• noun A compound (C₆Cl₄O₂) produced by the action of chlorin on aniline, phenol, salicin, and other allied bodies.

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

• noun (Chem.) A yellow crystalline substance, C6Cl4.O2, regarded as a derivative of quinone, obtained by the action of chlorine on certain benzene derivatives, as aniline.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A quinone with the molecular formula C6Cl4O2, used as a fungicide.