Ion-neutral-neutral complexes in unimolecular reactions: formation of proton-bound alkanol pairs from alkoxylated oxonium ions

The proton-bound alkanol pairs, [ROH . . .H+. . .R'OH], were generated in t he unimolecular fragmentation reactions of alkoxylated oxonium ions ROCH2-O +(R')(R") (where R, R'=CH3 or C2H5; R"=t- or iC(4)H(9)). By means of collis ion-induced dissociative ionization mass spectrometry, the neutral counterp art of this reaction was identified to be a C5H8 hydrocarbon molecule. It i s proposed that the reactions proceed through an intermediate ion-neutral c omplex in which two neutral alkanol molecules are associated with the 1,1-d imethylallyl cation, CH2=CH-C+(CH3)(2); the subsequent proton transfer lead s to the formation of the proton-bound alkanol pair and neutral 2-methylbut a-1,3-diene (C5H8). This is the first three-component intermediate "ion-neu tral-neutral" complex (where the ion is not a proton) identified in the uni molecular fragmentation of covalently-bonded organic ions in the gas phase.