Nitrogen-14 nuclear quadrupole resonance spectra of substituted nitrobenzenes

Abstract

The 14N nuclear quadrupole resonance spectra have been measured for nitrobenzene and nine substituted nitrobenzenes. The experiments were carried out at 77 K, using the double-resonance, level-crossing technique. The 14N signals for the −NH 2 groups of m-and p-nitroaniline were also observed. The quadrupole coupling constants for the nitro group nitrogens vary from 1493 kHz for p-nitroaniline (η = 0.292) to 1232 kHz for m-dinitrobenzene (η = 0.360). The dependence of e 2 Qq/ h upon the meta or the para substituent suggests that the substituents affect mainly the covalency in the nitrogen-carbon σ bond. A linear relationship is observed between e 2 Qq/ h and the Hammett substituent constants.