Conformations of highly hindered aryl ethers—XVIII : neighboring-ring anisotropy effects in poly(2,4-dinitrophenoxy)benzenes

A PMR study of ten poly-(2,4-dinitrophenoxy)benzenes and naphthalenes together with appropriate reference compounds, showed that (1) relatively long-range anisotropic effects are observed; (2) these are roughly additive when several benzene rings are present; (3) in the absence of steric effects there is no preference between syn and anti dispositions of substituting rings about the central ring; (4) concerted libration and concerted rotation occur freely even in highly substituted diaryl ethers; and (5) a twist conformation is preferred about the individual ether links.