B. S. Andonovski* and G. M.  Stojković
Institute of Chemistry,  “St. Cyril and Methodius University, P.O. Box 162, 91001 Skopje, Macedonia
 

ABSTRACT

Protonation of indole and 3-acetylindole in phosphoric and hydrochloric acid  solutions  was studied by UV spectroscopy. We present pKa  values obtained by the CVA (Characteristic Vector  Analysis) method. From the data, pKa values for protonation were obtained by using the Hammett's equation: pKa = H0 + log[c(BH+)/c(B)]. The dissociation constants and solvent parameter m* were obtained by  application of the Excess Acidity Method.  The position of protonation is discussed.

Key words: UV spectra, indole, 3-acetylindole, protonation, dissociation constants, Hammett Acidity Function Method, Excess Acidity Method, Characteristic Vector  Analysis.