The first starting material, 1H-2-acetylbenzimidazole, 4, was synthesized by o-phenylenediamine, 1, and lactic acid solution, 2, in hydrochloric acid medium on the first step than, oxidation reaction was performed by CrO 3 in acetic acid medium on the second step. The last starting material, ethyl 2-(2-acetylbenzimidazol-1-yl) acetate, 6, was synthesized by using first starting material, 4, ethyl 2-bromoacetate, 5, and K 2 CO 3 in acetone medium. The target compound, pyrido[1,2-a] benzimidazole-2,4-dione, 7, was synthesized by using the last starting material, 5, in sodium ethoxide medium. The compound, 7, can be found in two forms which are keto and enol which would be evaluated in this study. For the evaluation, it was performed some spectroscopic studies. In addition, it was evaluated experimentally obtained acidity constant, pK a value and tautomeric equilibrium of the compound, 7, by using ultraviolet-visible (UV-Vis) spectrophotometer. All of these studies have shown that the valid form of the compound, 7, is keto form.