N.m.r. spectra and conformations of 9,10-dihydroanthracenes

Abstract

The preparation of a series of substituted 9,10-dihydroanthracenes is described and their proton n.m.r. spectra are discussed. It is suggested that the trans-isomers of 9,10-dialkyl-9,10-dihydroanthracenes, substituted in the 9,10- or peri-positions adopt a planar ring conformation with the 9,10-dialkyl substituents placed over the ring. It is further suggested that the highfield signal of the β-protons of the 9,10-dialkyl substituents is due partly to the magnetic anisotropy of the aromatic rings, and partly to the magnetic anisotropy of the carbon–carbon bonds from the alkyl groups to the 9-and 10-positions in the central ring.