Effect of Solution Environment on the Absorption Maxima of Schiff Bases of Retinal*

Abstract— –Preliminary examination of the effect of solution environment on the electronic absorption spectrum of N‐retinylidene‐n‐butylamine(I) is reported. It is established that small amounts of CO 2 dissolved in certain solvents cause the formation of the conjugate acid of I. This reaction is shown to be dependent on temperature and the concentration of CO 2 . The pK b of I in aqueous buffer was measured spectrophotometrically and found to be 8.71. Salts of I were prepared in a number of ways and their spectra were determined in selected solvents. The Λ max varies with method of preparation, and only one method gives reproducible results. The Λ mnx is a function of the solvent in which the spectrum is determined. It was also found that the absorption maximum in wavenumbers is proportional to the negative logarithm of acid concentration.