Potentiometric Study of Acid−Base Equilibria of 3,5-Disubstituted 1,2,4,5-Oxadiazaboroles in Nonaqueous Media

The protonation constants of the amino nitrogens of some substituted 1,2,4,5-oxadiazaboroles have been determined in acetic acid by means of potentiometric titration with perchloric acid. pK_a values of the title compounds were interpreted on the basis of structural effects due to the substituents and the main skeleton by plotting pK_BH⁺ value versus Hammett constants. Good correlations between pK_BH⁺, σ constants, and δ_CN and δ_NH values were also obtained.