The unimolecular decompositions of the geometrical isomers maleamide (
cis-NH
2COCH=CHCONH
2;
1, MW: 114) and fumaramide (
trans-NH
2COCH=CHCONH
2;
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 NH
2 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, CH
2=CHCONH
2, which is formed by hydrogen atom migration from NH
2 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 CONH
2 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-NH
2]
+ ions decompose further by the losses of H
2O 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.
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