Acidity Scale in 1,2-Difluorobenzene

Equilibrium Brønsted acidity measurements have been established in 1,2-difluorobenzene (1,2-DFB), both in terms of acid pK _a values measured using UV-vis spectrophotometry and unified pH (pH_abs) values measured using differential potentiometry. The pK _a values of 137 acids were obtained in 1,2-DFB, of which 33 have been directly measured, spanning 15 orders of magnitude of acidity. The rest have been estimated using pK _a values in other solvents (acetonitrile, 1,2-dichloroethane). The pK _a values have been anchored to the computational pK _a values of 9 compounds. An experimental pH_abs scale spanning more than 10 orders of magnitude has been established and aligned with the aqueous pH scale, resulting in a ${pH}_{abs}^{H_{2}O}$ range from -0.6 to 10.0. The potentiometrically measured ${pH}_{abs}^{H_{2}O}$ values and ${pH}_{abs}^{H_{2}O}$ values calculated independently from the experimental pK _a values anchored to computational reference values agree well, which demonstrates the solid foundation of the underlying theory. These results open the possibility of quantitatively describing and measuring acid-base processes in 1,2-DFB, including potentiometric and UV-vis spectrophotometric ${pH}_{abs}^{H_{2}O}$ measurement.