A mechanistic study of the prominent loss of H2O from ionized 2-hydroxyaminoethanol

Tandem mass spectrometry experiments on the HCl salt of 2-hydroxyaminoethanol reveal that low-energy ions HOCH2CH2NHOH+ dissociate by loss of H2O with remarkable efficiency (c. 10%). Analysis of its high energy collision-induced dissociation (CID) mass spectrum leaves little doubt that the resulting m/z 59 ion is the cyclic 1,2-oxazetidine ion, whose elusive neutral counterpart has not yet been identified by experiment.A mechanistic analysis using the CBS-QB3 model chemistry indicates that the dissociation chemistry of HOCH2CH2NHOH+ is entirely different from that of the structurally related ions HOCH2CH2ONH2+ and HOCH2CH2OH+. It involves a 1,5-H transfer in one of its stable conformers that leads to a hydrogen-bridged radical cation of the 1,2-oxazetidine ion and a water molecule. In support of this proposal the isotopologues DOCH2CH2NDOD·DCl and HOCH2CD2NHOH·HCl, upon ionization (almost) exclusively lose D2O and H2O, respectively.