Einfluss der Orientierung von Substituenten auf die chemische Verschiebung von 13C. II. 13C‐NMR.‐spektroskopische Untersuchung von substituierten Spiro [cyclopropan‐1′,9‐fluorenen]

Effect of the Orientation of Substituents on the Chemical Shift of 13 II. 13C‐NMR. Study of Substituted Spiro [cyclopropane‐1′, 9‐fluorenes] The 13C‐NMR. spectra of spiro[cyclopropane‐1′, 9‐fluorenes] substituted at the cyclopropane ring have been assigned, largely with the aid of selective proton decoupling. The effects of the substituents upon the chemical shifts of the aromatic carbons are orientation dependent. the effects of cis‐substituents on γ‐carbon atoms are large and negative (inducing high field shifts), those of trans‐substituents smaller and dependent on the electron donor/acceptor properties of the substituents. The effects on δ‐carbon atoms in close proximity of the substituents are large and positive; they are interpreted in terms of electric field effects.