The title ion-molecule reaction has been proposed to play an important role in interstellar chemistry if it yields acrylonitrile ions CH2=CH-C N center dot+. This question was probed by examining the formation of HC CH center dot+ and HCN from low-energy ions CH2=CH-C N center dot+ and related isomers, using tandem mass spectrometry based experiments (D and C-13 labelling) in conjunction with model chemistry calculations (CBS-QB3/APNO). We conclude that the title reaction is a barrierless multistep rearrangement that may not effectively compete with the straightforward formation of stable distonic ions HC=CH-N CH center dot+ from HC CH center dot+(ion)-HCN(dipole) encounter complexes. (C) 2007 Elsevier B.V. All rights reserved.