Proton magnetic resonance spectra of the atropisomers of ortho-hexaphenylene

Abstract

The structures of the atropisomers of o-hexaphenylene are confirmed by their proton magnetic resonance spectra. The centrosymmetrical isomer 1a gives rise to an AA′BB′ spectrum, whereas the helical isomer 1b displays an AA′BB′ spectrum for two of its aromatic rings and an ABCD for the remaining four rings. Long-range coupling between the AA′BB′ and ABCD parts of 1b leads to a tentative assignment of the protons. An analysis of the spectrum of o-tetraphenylene (2) is also given.