Ring-chain tautomerism of halogenated phenolphthaleins: vibrational spectroscopic and semiempirical MO study

摘要

Ring-chain tautomerism of halogenated phenolphthleins and the effect of halogen substitution have been studied yb vibrational spectroscopic and semiempirical MO methods. The vibrational spectra indicate that the content of the colored species (carboxylate form) increases on the substitution of the isobenzofuranone ring, whereas the colorless species (lactone form) becomes dominant on the substitution of phenolic rings. MO calculations have revealed that the substitution of either ring does to change the basic property of the electronic transition of the colored species and that the relative stability of both forms is dependent on the substitution type in accord with the results of the vibrational study.