First Examples of Fluorinated and Chlorinated Polycyclic Aromatic Hydrocarbon (PAH) Dications from Benzo[<i>a</i>]pyrene, Pyrene, and Their Alkyl-Substituted Derivatives
作者:Kenneth K. Laali、Mutsuo Tanaka、Poul Erik Hansen
DOI:10.1021/jo980839l
日期:1998.11.1
Two-electron oxidations (SbF5/SO2ClF) of 6-fluoro-benzo[a]pyrene, 3, 6-chloro-benzo[a]pyrene 4, and their corresponding 7-methyl derivatives 5 and 6 as well as 1-fluoropyrene,;7, 1-chloropyrene, 8, and 1-fluoro-2,7-di-tert-butylpyrene, 9, allowed the charge delocalization mode, substituent effects, one-bond and long-range C/F coupling constants, and the tropicity of the resulting persistent PAH dications to be examined by NMR for the first time. For comparison, detailed NMR studies of the dications of 7-methylbenzo[a]pyrene, 2, and the parent benzo[a]pyrene, 1, are also reported. Total deshieldings Sigma Delta delta C-13 in the resulting dications are ca. 195-211 ppm/e for the benzo[a]pyrenium and ca. 200-209 ppm/e for the pyrenium dications, respectively. Their AM1-calculated Delta Delta H(f)degrees values are between 421 and 427 kcal/mol and 444 and 449 kcal/mol, respectively, well within the previously predicted dication formation limit of 463 +/- 4 kcal/mol.