COLLISION-INDUCED DISSOCIATIONS OF CARBANIONS IN THE GAS-PHASE - THE FORMATION OF VINYLIDENE CARBENE INTERMEDIATES FROM DEPROTONATED PROP-2-YNYL ETHERS

Evidence is presented which suggests that the anionic isomers MeO-CH2- C=C- and CH2=C=C--OMe, upon collision activation in the gas phase, fra gment through the vinylidene carbene intermediate [(CH2=C=C:)MeO(-)]. In particular, the intermediate eliminates CH2O and MeOH to form C3H3- and C3H-, respectively. Ah initio calculations indicate that the latt er ion has a ground state triplet structure with 'allenic' type geomet ry.