Evidence of HF Loss in C or C^- + C₆F_xH_6-x (1 ≤ x ≤ 5) Reactions

Patterns of anions produced by passing benzene and fluorobenzenes through a photoemission ion source show evidence of carbon addition with subsequent -H or HF loss. We recently reported a study of the fulvenallenyl structures of C₇F_xH_5-x ^- (0 ≤ x ≤ 2) formed in the former reaction. In this follow-up study, we report the anion PE spectra of the C₇F_xH_4-x^- (0 ≤ x ≤ 4) anions. We present experimental evidence that HF loss is necessary for C₇F_xH_4-x^- (0 ≤ x ≤ 4) formation, and calculations predict the reactions to be thermodynamically favorable. Based on a comparison between the experimental spectra and computational results on the anion and neutral, we conclude that two distinct C₇F_xH_4-x^- structures are formed. One structure resembles a fulvenallenyl structure that has undergone deprotonation from the acetylenic group, and the other is a cumulenic or other chain structure. The former is more stable than the latter except in the case of C₇F₄^-. Results of calculations suggest that the cumulenic structure becomes increasingly stable with fluorination.