The hydrogen-bridged radical cation [NH2CO⋯H⋯OCHCH3]+ and its dissociation by proton-transport catalysis

The title ion (HBRC-1) is an easily accessible hydrogen-bridged radical cation when generated by the decarbonylation of ionized ethyl oxamate, NH2COCOOC2H5.Tandem mass spectrometry experiments and CBS-QB3 model chemistry calculations agree that HBRC-1 dissociates into HC(OH)NH2+ +CH3CO by proton-transport catalysis. Its CH3CHO component catalyzes the isomerization NH2–C–OH+→NH2C(O)H+ and the ensuing intermediate [NH2C(O)H⋯OCHCH3]+ loses CH3CO by a facile proton transfer.In support of this, lactamide ions ND2C(O)CH(OD)CH3+ dissociate into DC(OH)ND2+ +CH3CO via the HBRC-1 isotopologue [ND2CO⋯D⋯OCHCH3]+. HBRC-1 also plays a key role in the decarbonylation of its isomer ionized urethan, NH2COOC2H5.