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

Abstract

Tandem mass spectrometry experiments on the HCl salt of 2-hydroxyaminoethanol reveal that low-energy ions HOCH 2CH 2NHOH + dissociate by loss of H 2O 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 HOCH 2CH 2NHOH + is entirely different from that of the structurally related ions HOCH 2CH 2ONH 2 + and HOCH 2CH 2OH +. 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 DOCH 2CH 2NDOD·DCl and HOCH 2CD 2NHOH·HCl, upon ionization (almost) exclusively lose D 2O and H 2O, respectively.