Methyl fluoride cluster beams, (CH 3F) n ionized by electron impact (EI) yield fragmentation patterns consisting solely of protonated parent ions plus ionic fragments produced by ejection of closed-shell molecules (e.g., HF, H 2, F 2, CH 4, in various combinations) therefrom. These ionic fragments result from extensive intramolecular rearrangement within the excited, solvated CH 3F + ion. The major reactive processes are rationalized in terms of known gas phase bimolecular ion-molecule reactions, including those of the dimethylfluoronium ion.