Fast-atom bombardment mass spectra of beta-nitrostyrene derivatives give rise to abundant M+. and [M + K](+) ions and exhibit a fragmentation pattern attributable to the presence of a nitro group, Collision-induced decomposition (CID) of their [M + H](+) ions reveals an additional fragmentation involving oxygen migration to the double bond and leading to the protonated aldehyde. This oxygen migration is the predominant process in the CID of the [M + Li](+) adducts which exhibit ions corresponding to the lithiated aldehyde and to elimination of the neutral aldehyde. (C) 1997 by John Wiley & Sons, Ltd.
