SUMMARY
N-[(2-oxoindolin-3-ylidene)-2-oxiacetyl] amino acids reactive ability was investigated at reversible conditions by studying their acid-base properties in binary dioxane-water (60 volume % of dioxane) solvent at 25°C. The experimental compounds were proven to be weak dibasic acids. Their pKa magnitudes were determined by Noyers method. The correlation of these magnitudes to both of the reactive sites (COOH- and OH-groups) was performed. Each CH2- prolongation step of the polymethylene chain length was shown to weaken acidity at both reactive sites ionization. Hammett correlation equations (pKa1,2 – f(s)) were calculated for N-[(2-oxoindolin-3-ylidene)-2-oxiacetyl] amino acids which allows to predict acid-base properties of these homological series compounds. Low susceptibility of the reactive sites towards polymethylene chain prolongation was established. The obtained results are being used to QSAR-analyze the compounds of these iso-structural series by mathematical modeling.