The gas-phase unimolecular reactions of C 2 D 5 CHFCl molecules with 94 kcal mol −1 of vibrational energy have been studied by the chemical-activation experimental technique and by electronic-structure computations. Products from the reaction of C 2 D 5 CHFCl molecules, formed by the recombination of C 2 D 5 and CHFCl radicals in a room temperature bath gas, were measured by gas chromatography− mass spectrometry. The 2,1-DCl (81%) and 1,1-HCl (17%) elimination reactions are the principal processes, but 2,1-DF and 1,1-HF elimination reactions also are observed. Comparison of experimental rate constants to calculated statistical rate constants provides threshold energies. The potential surfaces associated with C 2 D 5 (F)C: + HCl and C 2 D 5 (Cl)C: + HF reactions are of special interest because hydrogen-bonded adducts with HCl and HF with dissociation energies of 6.4 and 9.3 kcal mol −1 , respectively, are predicted by calculations. The relationship between the geometries and threshold energies of transition states for 1,1-HCl elimination and carbene:HCl adducts is complex, and previous studies of related molecules, such as CD 3 CHFCl, CD 2 ClCHFCl, C 2 D 5 CHCl 2 , and halogenated methanes are included in the computational analysis. Extensive calculations for CH 3 CHFCl as a model for 1,1-HCl reactions illustrate properties of the exit-channel potential energy surface. Since the 1,1-HCl transition state is submerged relative to dissociation of the adduct, inner and outer transition states should be considered for analysis of rate constants describing 1,1-HCl elimination and addition reactions of carbenes to HCl.