Solvent effects on the conformations of ortho-nitroanilines

Abstract

Proton magnetic resonance spectroscopy has been used to examine the conformations of a number of ortho-nitroanilines in solution. In solvents of low polarity, intramolecular hydrogen bonding maintains the coplanarity of the nitro group and the aromatic ring, but in more polar solvents the nitro group is rotated from the ring plane and this change is evidenced by an upfield shift in the resonance position of the adjacent aromatic proton. The extent of rotation depends on the polarity of the solvent and on the structure of the amine.