Gas-phase bimolecular chemistry of the ż−CHNC and ż−CHCN radical anions

Abstract

The gas-phase ion/molecule chemistry of the ż−CHNC and ż−CHCN radical anions formed in the reactions of the O ż− ion with CH 3NC and CH 3CN respectively, has been studied by Fourier transform ion cyclotron resonance mass spectrometry. The gas-phase acidity, Δ H 0 acid, of the żCH 2NC radical is determined to be 1582 ± 10 kJ mol −1, while the żCH 2CN radical is considerably more acidic in the gas phase (Δ H 0 acid = 1563 ± 3 kJ mol −1). The ż−CHNC ion does not react with the parent compound by proton abstraction in accordance with the gas-phase acidity of CH 3NC, which is determined to be 1589 ± 8 kJ mol −1 on the basis of a proton-transfer equilibrium between −CH 2NC and CH 3OH. The ż−CHNC and ż−CHCN radicals anions react with HCO 2CH 2CH 3, CF 3CO 2CH 2CH 3, CF 3COSCH 2CH 3 and CH 3SSCH 3 to form product ions of the same type, but in significantly different abundance ratios. In particular, the reaction of the ż−CHNC ion with HCO 2CH 2CH 3 proceeds by loss of an ethoxy radical and an ethanol molecule from the collision complex, whereas the reaction of the ż−CHCN ion with this substrate results almost exclusively in elimination of an ethoxy radical.