Structural analysis of C 8 H 6 ˙ + fragment ion from quinoline using ion-mobility spectrometry/mass spectrometry.

This study investigated the structures of fragment ions derived from the quinoline (C 9 H 7 N) radical cation using ion-mobility spectrometry and mass spectrometry. Ion mobility and mass analysis revealed that C 8 H 6 ˙ + is the primary dissociation product resulting from the loss of HCN during collision-induced dissociation of the quinoline radical cation. The reduced mobility ( K 0 ) of the C 8 H 6 ˙ + fragment product in helium gas was measured over a range of reduced electric fields ( E / N = 20.8-27.4 Td) at room temperature. The experimental K 0 values indicated that C 8 H 6 ˙ + is a mixture of phenylacetylene and pentalene radical cations. Furthermore, quantum chemical calculations revealed two potential energy surfaces delineating the loss of HCN from the quinoline radical cation to form phenylacetylene radical cations.