2,2,2-Trifluoroethyl chloride, bromide, iodide but not fluoride react with thiolate ions in DMF under laboratory illumination at 30-50 o C to give the 2,2,2-trifluoroethylthiol derivatives in high yields. The acceleration by UV irradiation, suppression by p-dinitrobenzene or hydroquinone and detection of trifluoroethyl radical by ESR spectroscopy show that the reactions occur by S R N 1 mechanism. The initiation step may be spontaneous or thermal electron transfer between thiolate and halides because the reactions can occur in dark.