Synthesis and Keto-Enol Tautomerism in N-(2-Hydroxy-1-Naphthylidene)Anils.

New ligands of Schiff bases [(C17H12NOX), X = F, Cl, Br, I] have been synthesised. Intra-molecular hydrogen bonding and keto-enamine tautomerism have been studied using IR, 1H-NMR, 13C-NMR (DEPT), UV-Visible and GC-MS techniques. The UV-Visible spectra of the compounds have been investigated in different solvents, acidic and basic media. The compounds were in tautomeric equilibrium (enol-imine O–H[ctdot]N, keto-amine O[ctdot]H–N forms) in polar and nonpolar solvents. The keto-amine form was observed in basic solutions of DMSO, ethanol, chloroform, benzene, and cyclohexane, and in acidic solutions of chloroform and benzene, but not in acidic solutions of DMSO and ethanol. 1H-NMR and 13C-NMR and IR results showed that all Schiff bases studied favor the enol-imine form over the keto form in a weakly polar solvent such as deuterochloroform solution. [ABSTRACT FROM AUTHOR]