Infrared Multiple Photon Dissociation Spectroscopy of Protonated Cyameluric Acid.

The present study reports the first structural characterization of protonated cyameluric acid ([CA + H]) in the gas phase, which paves the way for prospective bottom-up research on the condensed-phase chemistry of CA in the protonated form. A number of [CA + H] keto-enol isomers can a priori be produced as a result of protonation at available N and O positions of precursor neutral CA tautomers, yet ab initio computations predict different reduced [CA + H] isomer populations dominating the solution and gas phases that are involved in the ion generation process (i.e.