AbstractStereoelectronic factors allow facile Cl˙ atom loss from theexo‐6‐chloro‐2‐norbornanone radical cation but not from theendo‐6‐epimer. The predominant primary reaction in theendo‐6 and in theexo‐5 andendo‐5 compounds is HCl elimination. While CI˙ elimination occurs with skeletal reorganization, HCl loss, at least in part, does not. The 5‐chloro isomers undergo a regiospecific McLafferty rearrangement which occurs relatively slowly in competition with Cl˙ and HCl loss. The use of energy‐resolved forms of tandem mass spectrometry provides considerable detail regarding the unimolecular fragmentatio