2‐(4′‐Substituted) phenylisatogens: Analysis of 13 C substituent chemical shifts

The 13 C NMR spectra for eight 2‐(4′‐substituted)phenylisatogens were determined at 30°C in CDCl 3 . Analysis of the ipso ‐carbon SCS values was carried out using the well known DSP and DSP‐NLR models. Changes in the 13 C SCS values for the carbon atoms in the isatogen moiety suggest that a small degree of inter‐ring mesomeric resonance is possible between the ring systems. A three‐parameter model, which give better overall agreement than either the DSP or DSP‐NLR models, is proposed for the ipso ‐carbon SCS. The question of whether or not the isatogen moiety exhibits amphielectronic behaviour is still unresolved.