15N and 17O NMR spectra of some nitrogen- and oxygen-containing polyfluoroaromatic compounds

Abstract

The effect of substitution of hydrogen by fluorine on the 15N and 17O NMR chemical shifts in N-sulphinylarylamines, azoxy- benzenes, C,N-diarylnitrones and aromatic azomethines has been studied. Changes in nitrogen screening are controlled mainly by the radial factor <r −3> 2p(N), which depends on the electron density on nitrogen, those in oxygen screening — by the two factors, the excitation energy ΔE −1 and the radial factor <r −3> 2p(0), which may operate in the same or opposite directions. The 15N and 17O NMR spectra of the above compounds did not show any specific effects of perfluorination.