CALCULATION OF PROTON CHEMICAL-SHIFTS OF [14]-ANNULENE AND [18]-ANNULENE

The ring current and local anisotropic contributions of the π electrons and the σ core to the proton chemical shifts of [14]- and [18]annulene are calculated within the π theory. It is shown that the calculated shifts can be matched with the observed ones only if a non-planar distorted structure for [14]annulene and a (nearly) planar structure with no appreciable bond length alternation is assumed for [18]annulene. © 1979.