An experimental study of the ion/molecule association reactions in mixtures of methyl halide and dimethyl sulfide has been performed. MS/MS metastable and collision-induced dissociation experiments were performed on each [C3H9SX](.+) association product (X = I, Br, Cl, F) in order to determine structural conformations and to investigate reaction fragmentation pathways. For X = I, Br, and Cl, a two-center three electron atomic connectivity for the association adduct giving the following structure [CH3X therefore S(CH3)(2)](+) was observed. For X = F, the data suggests an F-H-S-bonded association adduct, [CH2F-H-S(CH3)(2)](.+). Kinetic energy release distributions were measured for metastable products whenever possible. Furthermore, density functional theory and unimolecular kinetic modeling were carried out to further probe the potential energy surfaces of these radical cations.