The reagent removes pairs of H atoms from organic molecules.  The stoichiometry of its action is illustrated by the conversion of tetralin to naphthalene:
:2 CCl(CN)O + CH → 2 CCl(CN)(OH) + CH
The resulting hydroquinone is poorly soluble in typical reaction solvents (dioxane, benzene, alkanes), which facilitates workup.
Solutions of DDQ in benzene are red, due to the formation of a charge-transfer complex.