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RESEARCH PRODUCT

Nitrogen-15 NMR Studies on Hydrazines. 2— Substituent Effect Analysis inortho-Substituted Phenylhydrazines and Anilines

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15N and 13C NMR spectra of some ortho-substituted phenylhydrazines were measured at natural isotope abundance in DMSO-d6 solutions. The substituent present exerts a larger effect on the chemical shift of the nitrogen atom directly bound to the aromatic ring (N-1), the second one (N-2) showing an attenuated trend of similar sign. Contrary to what observed for para and meta isomers, the cross-correlation between N-1 and N-2 SCS values of ortho-substituted phenylhydrazines is not satisfactory; on the other hand, N-1 SCSs show a reasonably good linear regression with the σR− constants. As expected, no correlation was found between N-1 and C-1 or H-1 SCS values. Correlations between 13C and 15N chemical shifts of the title compounds with those of ortho-substituted anilines and of monosubstituted benzenes are also reported. Multiparameter regression analysis carried out on a large range of ortho-substituted anilines gave satisfactory results in the TSP treatment of C-1 and C-2 chemical shifts. One-bond 15N–1H coupling constants of ortho-substituted phenylhydrazines and ortho-substituted anilines well correlate with σp− constants.