Solvent effects on the ultraviolet absorption spectra of o-, m-, and p-Hydroxybenzylideneimines

Abstract

The ultraviolet absorption spectra of the mono-salicylideneimines of ethylamine, ethanolamine, and n-butylamine and of the bis-salicylideneimines of ethylenediamine, trimethylenediamine, and 1,3-diaminopropan-2-ol have been separately examined in various solvents: water, absolute ethanol, dioxan, and cyclohexane. A comparison of these spectra with those of the N-methylimines of m- and p-hydroxy-benzaldehydes in similar solvents indicates that the o- and p-hydroxybenzylideneimines exist mainly as the dipolar keto amines in very polar, hydrogen-bonding solvents whereas the m-isomers exist mainly as the enol imine tautomeric form in all solvents.