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

Harig M, Kuck D. Mass spectrometric fragmentation of di-, tri-, and hexaquinane-fused dimethyl muconates induced by single and double electron ionization. ARKIVOC. 2020:9-19.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)-C-center dot, from the molecular radical cations, M center dot+. 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)-C-center dot 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. [GRAPHICS]