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Acidity Scale in 1,2-Difluorobenzene.

John Paulo Samin¹, Helerin Roomet¹, Märt Lõkov¹

¹Institute of Chemistry, University of Tartu, Ravila 14a, Tartu 50411, Estonia.

|June 1, 2026

Summary

This summary is machine-generated.

This study establishes Brønsted acidity measurements in 1,2-difluorobenzene (1,2-DFB), determining acid pKa values and a unified pH scale. These findings enable quantitative analysis of acid-base reactions in 1,2-DFB.

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Published on: February 20, 2020

Area of Science:

Physical Chemistry
Acid-Base Chemistry
Solvent Effects

Background:

Accurate measurement of Brønsted acidity is crucial for understanding chemical reactions in various solvents.
1,2-difluorobenzene (1,2-DFB) presents unique solvent properties that necessitate established acidity scales.
Previous studies lacked comprehensive acidity data and unified pH scales for 1,2-DFB.

Purpose of the Study:

To establish equilibrium Brønsted acidity measurements in 1,2-difluorobenzene.
To determine acid pKa values and create a unified pH scale (pHabs) in 1,2-DFB.
To enable quantitative description and measurement of acid-base processes in this solvent.

Main Methods:

Acid pKa values were measured using UV-vis spectrophotometry.
Unified pH (pHabs) values were determined using differential potentiometry.
pKa values were obtained for 137 acids, with 33 directly measured, and others estimated from acetonitrile and 1,2-dichloroethane data, anchored to computational values.

Main Results:

Experimental pKa values for 137 acids in 1,2-DFB were obtained, spanning 15 orders of magnitude of acidity.
An experimental pHabs scale was established, covering over 10 orders of magnitude and aligned with the aqueous pH scale (pHabsH2O range: -0.6 to 10.0).
Potentiometrically measured pHabsH2O values showed excellent agreement with those calculated from experimental pKa values, validating the theoretical framework.

Conclusions:

The study successfully established a robust framework for measuring Brønsted acidity in 1,2-DFB.
The developed pHabs scale and pKa data facilitate quantitative analysis of acid-base equilibria in this solvent.
These findings pave the way for advanced studies on acid-base chemistry in fluorinated aromatic solvents.