LAUSR

Abstract Pyrazine‑2‑amidoxime (PAOX) is a prototypical sp2-hybridized amidoxime. Although, we described first time in details PAOX structure in solid state, the profile of PAOX behavior in aqueous solution still needs to be improved. While, acid-base properties of PAOX have been tried to define just once, the presented description was not complete and based only on the results of potentiometry during complexometric studies. The selection of method gives rise problems to observation the protonation or deprotonation processes of compound studied. Due to above, the presented studies show first time the complete description of PAOX acid-base properties by obtaining its pKa, solubility, partition (P) and distribution (D) coefficients using various methods. Among them, experiments: potentiometry; UV spectrophotometry by using Hammett's function and pH-metric titrations; cyclic voltammetry (CV) with glassy carbon electrode (GCE) and with GCE electropolymerized by poly‑ l ‑glycine (PGGCE); 1H NMR and theoretical calculations (DFT). Generally, combined four types of experimental and theoretical methods were used to estimate PAOX macro acidic-dissociation constants values. Moreover, log P and log D were determined spectrophotometrically and calculated also by DFT methods. No previous reports were found in the presented form regarding the complete drug-like properties, including negative together with positive values of pKa. Additionally, we proved by our electrochemical results that the quantitative analysis of PAOX do not need the special conditions of the electrode used in research. Hence, the comparison of our results to those described in the literature about analysis made for others, amidoxime derivatives.