Abstract:
The cis-9, 10-dialkyl-9, 10-dihydroxyanthracenes exist in the boat conformation where the bulkier alkyl groups are pseudoaxial, the C11-protons are somewhat shielded by the magnetic anisotropy of the benzene rings, but the C12- and C13- protons remain unaffected. In the trans-isomers, the central ring is flat, at least on an n.m.r. time scale, because the resonances of both the alkyl groups are equivalent lh flipping from pseudo-axial to pseudo- equatorial positions, the C12- and C-13-protons pass through a region of maximum shielding when the tricyclic ring system is planar. The C11-protons in all the cis-isomers resonate at higher field than those in the corresponding trans-isomers and vice-versa for the C12-and C13-protons.
Page(s):
89-108
DOI:
DOI not available
Published:
Journal: Pakistan journal of scientific research, Volume: 18, Issue: 1--2, Year: 1989