Conformation of the −NH2 group in a single crystal of p-chloroaniline as determined by combined Zeeman effects on the 35Cl and 14N nuclear quadrupole resonances

Abstract

The Zeeman effect on the nuclear quadrupole resonance of both ³⁵Cl and ¹⁴N nuclei in a single crystal of p‐chloroaniline has been studied at room temperature. A spectrometer was employed which was capable of working at the resonance frequency of either nucleus without altering the position of the crystal. Novel features of the spectrometer were both a frequency stabilizing apparatus working at the ¹⁴N resonance frequency and the attachment of an electronic computer for direct and accurate ``on‐line'' determination of spectral parameters. The relative orientations of the electric field gradient tensors on both nuclei have been obtained. Furthermore, by studying the ¹⁴N linewidth dependence on the static magnetic field orientation, information has also been gained about the position of the −NH₂ protons in the electric field gradient tensor principal axes mainframe. Some remarkable experimental results can be interpreted theoretically when the treatment of the magnetic dipole interaction between ¹⁴N and ¹H in the −NH₂ group is pushed beyond first order. Analogous information has been gained by also studying a single crystal of p‐bromoaniline.