Substituenteneffekte auf die NMR‐Spektren von Pentafulvenen . ( 13 C, 13 C)‐NMR‐Kopplungskonstanten ( 1 J (C, C))

Substituent Effects on NMR Spectra of Pentafulvenes. 13 C, 13 C‐NMR Coupling Constants ( 1 J (C, C)) 1 H‐ and 13 C‐NMR spectra of 6‐monosubstituted pentafulvenes 1 – 8 have been analysed, and 1 J (C, C) coupling constants have been determined from ID‐inadequate spectra of 13 C satellites. It turns out that 13 C, 13 C coupling constants of the ring C‐atoms, and especially J (1,2)/J(3,4) and J (2,3), reflect the extent of π delocalisation in the fulvene ring. With increasing electron‐donating capacity of the substituent R, J (1,2)/J(3,4) values are decreasing, while J (2,3) (and J (1,5)/ J (4,5) as well) are increasing, and linear correlations of Hammett substituent constants σ + and 1 J (C,C) values are obtained.