Collision-Induced Dissociation of Imidazolium-Based Zwitterionic Liquids

Fragmentation pathways of some imidazolium based zwitterionic liquids—3-(3-alkyl-1-imidazolio)-propane sulfonates and 3-(2-methyl-3-alkyl-1-imidazolio)-propane sulfonates—have been studied by tandem electrospray mass spectrometry and collision-induced dissociation. The relative abundances of the lowest energy fragment ions depend on the length of the alkyl chain at the ^IIN of the imidazolium ring and the cone voltage. The first fragment ions originate from the scission of C_{non aromatic}–N bond of compounds investigated, but with increasing collision energy, scission of C–C bonds occurs. Aggregates of the general formula [(M + H) _x + (M) _y ]⁺ (x;y = 1–2) formed. Methyl substituted zwitterionic liquids show higher molecular stability than 3-(3-alkyl-1-imidazolio)-propane sulfonates.