Collision-Induced Dissociation (CID) Spectra versus Collision Energy Using a Quadrupole Ion Trap Mass Spectrometer IV

—Dissociation of Ionized Maleamide and Fumaramide—

Abstract

The unimolecular decompositions of the geometrical isomers maleamide (cis-NH₂COCH=CHCONH₂; 1, MW: 114) and fumaramide (trans-NH₂COCH=CHCONH₂; 2, MW: 114) have been investigated by use of collision-induced dissociation (CID) spectra versus collision energy. These ions, 1^+· and 2^+·, show as primary fragmentation channels the losses of NH₂ and CONH to give the ions m/z 98 and 71, respectively, but the relative abundance of these ions is different with each other. This will be attributable to amide-amide interaction in cis-isomer. The fragment ions m/z 71 correspond to the molecular ion of acrylamide, CH₂=CHCONH₂, which is formed by hydrogen atom migration from NH₂ to ethylenic carbon in the molecular ions 1^+· and 2^+·, followed by CONH loss. The additional dissociation channels are observed for 2^+·, the losses CO and CONH₂ to give the ions at m/z 86 and 70, respectively. These two reactions were weak for 1^+·. These ions, except for m/z 71 ion, retain the structure difference between the geometrical isomers. The [M-NH₂]⁺ ions decompose further by the losses of H₂O and CO to generate the ions at m/z 80 and 70, respectively. The former reaction for 1 is different from that for 2. This reaction accompanies with double hydrogen atom transfers, and was not described in previous report.