A Quantum-Chemical Study of Prototropic Tautomerism in 1-Hydroxy-9,10- anthraquinones

The effect of substituents R on the tautomerism and electronic absorption spectra of 1-hydroxy-x-R-9,10-anthraquinones and 9-hydroxy-x-R-1,10- anthraquinones was studied by quantum-chemical and correlation methods. The former compounds (x ≠ 2) are more sensitive to substituent effects than the latter compounds. Examination of the fine structure of long-wave absorption showed that the experimental spectra of 1-hydroxy-x-R-9,10-anthraquinones contain no bands assignable to ana-quinoid forms.