DOES THE LOSSEN REARRANGEMENT OCCUR IN THE GAS-PHASE

Deprotonated hydroxamic acids and cognate systems undergo a number of rearrangement processes upon collisional activation. It is proposed that ions RCONBAROH undergo the Lossen rearrangement to form [(OCNR)HO-], and that this reactive intermediate may decompose to form the ionic products HO-, [(R - H)-NCO], NCO- and RNH-. Alternatively, hydrogen transfer yields RCONHO- which may undergo a three-centre reaction to produce RCO2NH-; this species may decompose to yield both RCO2- and [(R - H)CO2].-. Fragmentation processes have been investigated by both deuterium labelling and product ion studies.