Mesomeric and electromeric factors in the mononitronaphthylamines

Abstract

The electric dipole moments of the ten mononitronaphthylamines with the substituents in non-adjacent positions and the 1-nitronaphthalene and 1-naphthylamine have now been completed in the solvents—benzene and dioxan. Interaction moments have been calculated for the mononitronaphthylamines in each solvent and linear relationship with these and the corresponding σ values ensue for the following substituent position (i) homonuclear (ii) heteronuclear in quinonoid positions (iii) heteronuclear in non-quinonoid positions. The homonuclear isomers exhibit similar features to the m- and p-nitroanilines. The isomers of type (ii) provide direct evidence for the existence of quinonoid resonance forms and in two cases at least their increased contribution in dioxan as opposed to benzene solution. In particular, 5-nitro-1-naphthylamine appears to have a negligible quinonoid contribution in benzene but quite appreciable in dioxan. Thus, the behaviour brings out the electromeric nature of the solute molecule by intermolecular hydrogen bonding with the solvent. This effect appears to be significant only when the substituents are in quinonoid positions. Apart from substituents in such positions and small deviations, the isomers obey the relationship obtained by Smith and Walshaw1 for various m- and p-substituted anilines.