Determination of acidity constants of pyridines, imidazoles, and oximes by capillary electrophoresis.

The acidity constant in the form of pK a is one of the most important physicochemical quantities. There are prediction tools available for calculating the pK a , but they only deliver precise calculated values for a relatively small set of chemicals. For complex structures with multiple functional groups in particular, the error in the predicted pK a is high due to the application domain of the corresponding models. Thus, we aim to enlarge the dataset of experimentally determined pK a values using capillary electrophoresis. We, therefore, selected various pyridines, imidazoles, and oximes to determine the pK a values using the internal standard approach and the classical method. Especially oximes were not investigated in the past, and predictions for them include larger errors. Thus, our experimentally determined values could contribute to an improved understanding of various functional groups impacting the pK a values and serve as additional datasets to develop improved pK a prediction tools.