New [C 2 , H 3 , N, O] +˙ isomers: A metastable and collision‐induced fragmentation study

Metastable and collision‐induced fragmentation in a masspsectrometer were used to characterize several [C 2 , H 3 , N, O] +˙ isomers. CO 2 loss from ionized oxazolidine‐2,5‐dione yields the distonic ions H 2 CNHCO +˙ and HNCH 2 CO +˙ and not the cyclic isomer, . Kinetic energy relese measurement indicate that CO 2 loss from the molecular ions is accompanied by a significant barrier for the reverse reaction. In this respect the behavior of oxazolidine‐2,5‐dione parallels that of the isoelectronic compound sucinic anhydride. O(H)CC(H)NH +˙ kions are generated via CO loss from 2(3 H )‐oxazolone molecular ions. There is no evidence to support generation of the cyclic isomer, . For comparison, data wer obtained for the known isomers H 3 CNCO +˙ , H 3 COCN +˙ , H 3 CCNO +˙ , HOCH 2 CH +˙ H 2 NCCOH +˙ H 2 N(H)CCO +˙ and H 2 CC(H)NO +˙ . The H 3 COCN +˙ and H 3 CCNO +˙ structures were assigned to the m / z 57 fragment ions from methyl cyanoformate and acetohydroxamic acid, respectively.