M. Percino, V. Chapela, Omar Urzúa
Apr 15, 2007
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Journal
International Journal of Mass Spectrometry
Abstract
Abstract EI mass fragmentation of the 1,2-bis(6-methylpyridin-2-yl)ethane-1,2-dione and 1-(pyridin-2-yl)-2-(6-methylpyridin-2-yl)ethane-1,2-dione radical cations gave rise to a sequence of unexpected composite ion peaks. The molecular ion m / z 240 gives mass measurements of metastable ions at m / z 212 and 184 and the molecular ion m / z 226 gave peaks at m / z 198 and 170 resulting from the successive loss of two fragments of 28 mass units each, corresponding to CO. These fragmentations yield the products [CH 3 C 5 H 3 NCOC 5 H 3 NCH 3 ] + , [(CH 3 C 5 H 3 N) 2 ] + and [C 5 H 4 NCOC 5 H 3 NCH 3 ] + , C 5 H 4 NC 5 H 3 NCH 3 ] + , respectively, as confirmed by mass determination identification of the precursor ions and decomposition product ions. In addition, the prominent ions [CH 3 C 5 H 3 NC O] + , [O CNH 3 C 5 CH 3 ] + , [C 5 H 3 NC O] + and [O CNH 3 C 5 CH 3 ] + , arising from cleavage of the C C bond, were detected in similar abundance ratios for both fragments and the corresponding secondary fragments, which can be attributed to the dissociation of several ionized α-diketones. The ionized homologue α-diketone 1,2-dipyridyldione also exhibited a decarbonylation channel yielding the molecular ion m / z 212, and before losing CO gave peaks at m / z 184 and 156. The fragmentation of 1,2-diphenylethane-1,2-dione did not exhibit the same behavior. The results confirm that the green co-crystal obtained is a co-compound formed of 1,2-bis(6-methylpyridin-2-yl)ethane-1,2-dione and 1-(pyridin-2-yl)-2-(6-methylpyridin-2-yl)ethane-1,2-dione.