Mass spectrometric fragmentation of di-, tri-, and hexaquinane-fused dimethyl muconates induced by single and double electron ionization

The electron ionization mass spectra of nine muconic acid dimethyl esters that bear up to three muconate groups fused with a centropolycyclic di-, tri-and hexaquinane framework exhibit dominating fragmentation by loss of a methoxycarbonyl radical,  COOMe, from the molecular radical cations, M + .Pyrylio-annelated structures for the [M -COOMe] + ions are postulated in analogy to literature reports on simple muconic acids esters.The congeners bearing two or three dimethyl muconate groups lose also two  COOMe radicals after twofold ionization.The doubly charged fragment ions [M  2 COOMe] 2+ are proposed to contain two isolated pyrylium rings fused to the original tri-or hexaquinane core, thus representing polyaromatic distonic dications.

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