Energy Requirements for Remote Charge Site Ion Decompositions and Structural Information from Collisional Activation of Alkali Metal Cationized Fatty Alcohols

Collisional activation of long-chain fatty alcohols cationized with certain alkali metal cations results in decompositions originating remote from the site of charge. These charge-remote fragmentations, like the previously discovered reactions of fatty acid carboxylates, are structurally informative and fill a need in structural chemistry which is not met by spectroscopic methods such as NMR, IR, and UV–vis. The decompositions produce closed-shell organic ions containing the alkali cations and are analogous to those observed previously for fatty acid anions. There are two alkali metal ion containing radical cations which may be produced by remote fragmentation to give distonic ions. The decompositions clearly indicate double bond position for both monounsaturated and polyunsaturated fatty alcohols. However, fragmentation of homoconjugated polyunsaturated fatty alcohols is complicated by the presence of daughter ions representing cationization of the double bonds in addition to cationization of the terminal hydroxyl. The types of decompositions of the [M + Li]⁺, [M + Na]⁺, [M + K]⁺, and [M + Rb]⁺ ions of oleyl alcohol change smoothly, and the variations can be understood in terms of the gas-phase enthalpies of solvation for the alkali metal ions. On the basis of changes in fragmentation to favor release of the alkali metal cation, an estimate of 1.3–1.9 eV for the internal energy required for remote charge site decompositions is made.