Proton dissociation properties of arylphosphonates: Determination of accurate Hammett equation parameters

• Published in: Journal of pharmaceutical and biomedical analysis Vol. 143; pp. 101 - 109
• Main Authors: Dargó, Gergő, Bölcskei, Adrienn, Grün, Alajos, Béni, Szabolcs, Szántó, Zoltán, Lopata, Antal, Keglevich, György, Balogh, György T.
• Format: Journal Article
• Language: English
• Published: England Elsevier B.V 05.09.2017
• Subjects: Acids; Arylphosphonic acids; Hammett equation; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; NMR-pH titration; Organophosphonates - chemistry; pH-metric pKa measurements; pKa predictors; Protons; Hammett equation; pKa predictors; pH-metric pKa measurements; Arylphosphonic acids; NMR-pH titration; pK(a) predictors; pH-metric pK(a) measurements
• ISSN: 0731-7085; 1873-264X
• DOI: 10.1016/j.jpba.2017.05.038

[Display omitted] •Determination of the proton dissociation constants of arylphosphonic acid derivatives.•Comparison of our experimental values to predicted and formerly measured pKa values.•Hammett equations of proton dissociation of arylphosphonic acid derivatives were refined. Determination of the proton dissociation constants of several arylphosphonic acid derivatives was carried out to investigate the accuracy of the Hammett equations available for this family of compounds. For the measurement of the pKa values modern, accurate methods, such as the differential potentiometric titration and NMR-pH titration were used. We found our results significantly different from the pKa values reported before (pKa1: MAE = 0.16 pKa2: MAE=0.59). Based on our recently measured pKa values, refined Hammett equations were determined that might be used for predicting highly accurate ionization constants of newly synthesized compounds (pKa1=1.70–0.894σ, pKa2=6.92–0.934σ).