Resonace Raman Spectra of Acid-Base Indicators. II. Hydroxyarylazobenzene Derivatives

Abstract

The effects of pH on resonance Raman spectra of several hydroxyarylazobenzene-type acid-base indicators have been investigated. All the compounds examined show the azo-type spectra in basic solutions, while the neutral solution spectra are the azo-type for p-hydroxyphenyl compounds and the quinoid-type for α- and β-hydroxynaphthyl compounds. The spectrum of Tropaeoline O changes complicatedly along with the protonation and deprotonation on the pH change.