A series of aromatic and non-aromatic compounds such as sulfonamides, amides, phenols, oximes and pyrimidines were analyzed for their CID fragments and the molecular compositions of the key fragments were identified through accurate mass measurement using the LTQ Orbitrap mass spectrometer.

For sulfonamides, in general, when the sulfonamidenitrogen was attached to an aromatic ring, free radical fragment ions involving the aromatic amine due to the S-N bond cleavage were observed, unless more facile CID pathways were present and prevailed in the structure. For non-aromatic sulfonamides, free radical fragments were not observed in the test compounds.

Aromatic t-Bu and ether compounds normally generated a free radical fragment ion resulted from the loss of the methyl or ethyl free radical.

Free radical fragments were observed more rarely in the selected amides, pyrimidine and oxime compounds. The assignment of these free radical ions was all supported by the accurate mass measurement on the LTQ Orbitrap with a mass accuracy less than 5 ppm. One common theme among these compounds that showed free radical fragment ions is that the newly formed free radical is located at a position next to an aromatic ring which stabilizes this free radical.

To view/download the complete note, please use the link on the left of this page.