The reactions of 2,2,2-trifluoroethanethiol on Mo(110) were studied using temperature-programmed reaction, Auger electron, and infrared spectroscopies. The chemistry of trifluoroethanethiol on Mo(110) is quite complex and significantly different than that observed for ethanethiol. Most significant is the evolution at 265 K of trifluoroethyl radical from a saturation coverage of CF3CH2S-. Ethyl radical was not detected in the reaction of ethanethiol on Mo(110). The strong coverage dependence for trifluoroethyl radical evolution and models depicting trifluoroethyl thiolate orientation at saturation coverage strongly suggest that surface crowding plays a significant role in radical formation. The stability of the radical and the steric inhibition to finding an adsorption site explain the evolution of the radical into the gas phase. C-S bond hydrogenolysis, yielding trifluoroethane, and defluorination, yielding difluoroethylene, are of nearly equal importance in the reaction of trifluoroethyl thiolate, whereas C-S bond hydrogenolysis of ethyl thiolate to form ethane predominates. The C-S bond hydrogenolysis pathway is similar for the two thiols, occurring at approximately 300 K in both cases. Dehydrogenation and alkene elimination from CH3CH2S- occur at approximately 340 K, as the supply of surface hydrogen is depleted through hydrogen recombination. In contrast, defluorination and fluoroalkene elimination from CF3CH2S- occur over a wide temperature range, 200-520 K. The relative facility of difluoroethylene formation is rationalized in thermodynamic terms. The formation of difluoroethylene on Mo(110) is nearly thermoneutral, due to the comparable strengths of the C-F and Mo-F bonds and the stability of difluoroethylene.