Study of tautomeric transformations of 1,4,5,8-tetraaminoanthraquinone by electronic spectroscopy

Based on the example of 1,4,5,8-tetraamino-9,10-anthraquinone, a method is described for establishing the tautomeric compositions and sequences of tautomeric transformations that occur in known samples of quinones. An analysis of electronic absorption spectra shows that this substance is a dynamic equilibrium mixture of 4,5,8,9-tetraamino-1,10-anthraquinone and the imines tautomeric to it. The tautomeric compositions of different samples of matter differ and can contain 1,4,8-triamino-5-hydroxy-9,10- anthraquinone-10-imine, 4,8,9-triamino-10-hydroxy-1,5-anthraquinone-5-imine, 5,8-diamino-4,9-dihydroxy- 1,10-antraquinonediimine, and 8,10-diamino-5,9-dihydroxy-1,4- antraquinonediimine. Tautomeric equilibrium shifts can accompany not only chemical reactions but physical processes as well, so any investigation of the properties of substances without establishing their tautomeric compositions would be incorrect. © Pleiades Publishing, Ltd., 2013.