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Nitrogen‐15 NMR Studies on Hydrazines. 2— Substituent Effect Analysis in ortho –Substituted Phenylhydrazines and Anilines
Author(s) -
Mezzina Elisabetta,
Spinelli Domenico,
Chimichi Stefano,
Frenna Vincenzo,
Lamartina Liliana
Publication year - 1996
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/(sici)1097-458x(199612)34:12<1019::aid-omr19>3.0.co;2-f
Subject(s) - chemistry , substituent , chemical shift , nitrogen , carbon 13 nmr , coupling constant , ring (chemistry) , computational chemistry , nmr spectra database , stereochemistry , medicinal chemistry , organic chemistry , spectral line , physics , particle physics , astronomy
15 N and 13 C NMR spectra of some ortho ‐substituted phenylhydrazines were measured at natural isotope abundance in DMSO‐ d 6 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 σ R − constants. As expected, no correlation was found between N‐1 and C‐1 or H‐1 SCS values. Correlations between 13 C and 15 N 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 15 N– 1 H coupling constants of ortho ‐substituted phenylhydrazines and ortho ‐substituted anilines well correlate with σ p − constants.