Trifluoromethyl-substituted compounds are formed in a corona discharge or glow discharge plasma of trifluoromethyl radicals from an organic trifluoromethyl source. A substrate possessing easily replaceable ligands such as halogen or carbonyl, is initially contacted either in the plasma and within a short distance from a downstream visible edge of the plasma or outside of the visible portion of the plasma and within a short distance from the downstream visible edge, to effect a substitution of the halogen or carbonyl ligand on the substrate with a trifluoromethyl radical without substantial decomposition of the substrate.