NMR studies of complex formation between N-methyl morpholine and sulphur dioxide

Proton magnetic resonance spectra of methylene dichloride solutions containing N-methyl morpholine and sulphur dioxide have been studied as a function of temperature. Complex formation reduces the rate of interchange of magnetic sites via inversion at nitrogen but increases the rate of ring inversion. The conformational preference of the complex is discussed. It is suggested that interaction with SO₂ may be a useful general method of studying nitrogen inversion.