The Effect of Electron-Donating and Electron-Withdrawing Substituents on 1H- and 13C-NMR Chemical Shifts of Novel 7'-Aryl-Substituted 7'-Apo-β-carotenes

Article abstract of DOI:10.1002/hlca.19930760511

The synthesis of 7'-aryl-7'-apo-β-carotenes, where aryl (Ar) is Ph, 4-NO2C6H4, 4-MeOC6H4, 4-(MeO2C)C6H4, C6F5, and 2,4,6-Me3C6H2, is described.NMR Chemical shifts of all H- and C-atoms are presented, together with specific examples of the spectra.In contrast to 1H chemical shifts which, except for H-C(8') and H-C(7'), did not differ greatly from those of β,β-carotene, considerable variations in 13C chemical shifts were observed.Signals of the C(α) atoms of the polyene chain _nAr were shielded, those of the C(β) atoms were deshielded, with some exceptions when n = 1; the effects decreased with increasing n.