Nuclear magnetic resonance studies of six-membered rings. Part II. Chemical shifts and coupling constants in morpholine and piperazine derivatives

Abstract

The ¹H n.m.r. spectra of morpholine, piperazine, and their N-methyl derivatives have been measured at temperatures sufficiently low for the ring-inversion process to appear slow. The substituent dependence of the parameters obtained from analysis of these spectra is discussed. It is shown that the effects of nitrogen and oxygen substituents on chemical shifts are additive except when both substituents are adjacent to the same methylene group.