The two possible hydrogen abstraction reactions of F atoms with CHF2CH3(HFC-152a) have been studies by ab initio methods at UMP2/6-31G level with energy gradient technique. The reaction paths (i.e. the intrinsic reaction coordinate) of the reaction have been traced by numerical method. In addition, the theoretical rate constants and their ratio have been calculated by conventional and variational transition-state theory. The calculated rate constants and their ratio are in good agreement with experimental results.

Key words: FLUORINE, AB INITIO CALCULATION, REACTION RATE CONSTANT, TRANSITION STATE THEORY, DIFLUOROMETHANE, REACTION PATH