N-15 NMR - SUBSTITUENT EFFECT ANALYSIS IN PARASUBSTITUTED AND META-SUBSTITUTED PHENYLHYDRAZINES

N-15 NMR spectra of phenylhydrazine and of 14 para- and meta-substituted phenylhydrazines were measured at natural isotope abundance in DMSO-d6 solution. The substituent present exerts a larger influence on the chemical shift of the nitrogen atom directly bound to the aromatic ring (N-1) than on the second one (N-2), which shows an attenuated and inverted trend. The chemical shifts of N-1 and N-2 give a good cross correlation in both series of compounds if p-NO2 and m-F derivatives are excluded from the correlations of para- and meta-substituted phenylhydrazines, respectively. Moreover, N-1 SCS values show good linear correlations with Hammett substituent constants, with SCSs of directly bound hydrogen (H-1) and with aniline nitrogen SCSs. The results of dual substituent parameter analysis are also reported together with a comparison of C-13 and N-15 chemical shifts with those of monosubstituted benzenes and substituted anilines.