The 15N and 13C NMR study of Schiff bases of amino acids and their lithium salts in solid state and DMSO solution

The 13C, 15N NMR of Schiff bases and their lithium salts, derivatives of amino acids (glycine, alanine, phenylalanine, valine and leucine) and 2-hydroxynaphthylaldehyde in solid state and in DMSO have been measured. The results have shown that the Schiff bases and their lithium salts exist mainly as the proton transferred NH form in solid state and DMSO. The nitrogen atom is protonated by hydrogen originating from the phenolic group.