Absolute and general assignment of constitutional isomers by mass spectrometry: the case of methylpiperidines

ABSOLUTE AND GENERAL ASSIGNMENT OF CONSTITUTIONAL ISOMERS BY MASS SPECTROMETRY: THE CASE OF METHYLPIPERIDINES. An absolute method is described via mass spectrometry (MS) for the structural assignment of isomers within the class of methylpiperidines. The method explores both the unhnolecular and bimolecular gas phase behavior of structurally diagnostic fragment ions (SDFI). For the methylpiperidnes, the isomeric 2-methyl, 3-methyl and 4-methyl 2-azabutadienyl cations are found to function as SDH. These fragment ions are expected to be formed from all members within the class, to he stable and to retain the structural information of the precursor molecule, and to not interconvert into one another. To characterize these SDFI, both the collision induced dissociation (CID) in argon and bimolecular ion/molecule chemistry with ethyl vinyl ether were compared.