Analytical properties of the amidoxime group: VIII. Synthesis, spectral properties, potentiometric and thermometric behaviour of 3,5-dimethyl, 3-phenyl-5-methyl and 3,5-diphenyl-4-isoxazolylamidoxime

Three 4-isoxazolyl-3,5-disubstituted amidoximes have been obtained and several of their physicochemical properties have been studied. The p K a values have been potentiometrically determined, with each amidoxime having two protonation constants, one for low pH values (p K a 2.24–2.96), and one for high pH values (p K a 11.55–12.06). The thermometric behaviour of 3,5-dimethyl-4-isoxazolylamidoxime is studied in an ethanol/water mixture (50%, v v ) in order to evaluate the error in its thermometrie titration with HCl and the corresponding neutralization enthalpy at 25°C.