Stable Ion Studies of the Chrysene Skeleton. Protonation of Chrysene, 6-Halochrysenes, 6-Acetylchrysene, and 4H-Cyclopenta[def]chrysene: NMR Studies of Charge Distribution in Chrysenium Cations and AM1 Calculations

Abstract

Chrysene (1), 6-fluorochrysene (2), 6-chlorochrysene (3), and 6-bromochrysene (4) are cleanly monoprotonated in FSO3H·SbF5 (ca. 10:1)/SO2ClF at the C-12 position. 6-Acetylchrysene (5) is CO-protonated in FSO3H/SO2ClF with significant charge delocalization into the chrysene and provides a model for a C-6-protonated chrysenium cation. 4H-Cyclopenta[def]chrysene (6) is protonated at C-5 (site of bromination and acetylation). The observed chrysenium (methanochrysenium) cations are those predicted by AM1 to have the lowest energies. The NMR characteristics of the resulting arenium ions are discussed and the Δδ 13Cs are compared with AM1 calculated changes in charges [Δqc = qc(ion) − qc(neutral)]. Possible relationships between the charge delocalization path in chrysenium ions and metabolic activation of chrysenes by electrophilic pathways via the bay-region epoxide ring opening (→ PAH−DNA adduct) are evaluated.