AN INFRARED STUDY OF THE BASICITY OF NON‐AROMATIC IMINES: RELATION TO VISUAL PIGMENTS

Abstract
Abstract— The knowledge of the basicity of non‐aromatic Schiff‐bases is important for the interpretation of the photochemical primary step of vision. In order to obtain an estimate of it, the infrared spectra in chloroform d solution of a number of aliphatic amines, pyridine derivatives and non‐aromatic Schiff‐ bases have been measured. From the known pKa values of the aliphatic and pyridine bases and the free‐associated frequency shift (Av) of the C—D. N hydrogen bonds, the pKa values for the Schiff‐bases were inferred. They range from 6 to 8. 5, less basic than aliphatic amines but somewhat more basic than pyridine bases.
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