Research Article
Study of the Predicted Variation of the Acidity Constant (pKa) of a Family of Chlorophenols as a Function of Quantum Chemical Descriptors
Fatogoma Diarrassouba*,
Affoue Lucie Bede,
Kafoumba Bamba,
Nahosse Ziao
Issue:
Volume 10, Issue 2, December 2026
Pages:
19-33
Received:
27 September 2026
Accepted:
27 October 2026
Published:
28 October 2026
DOI:
10.11648/j.ijec.20261002.11
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Abstract: The acidity constant, or acid dissociation constant (Ka), is a quantitative measure of the strength of an acid in solution. It reflects the tendency of an acid to dissociate and release a proton (H⁺ or H3O+) to water. It serves as the equilibrium constant for the dissociation reaction of an acidic species within the context of acid-base reactions. The higher the value of Ka, the greater the extent of molecular dissociation in solution, and consequently, the stronger the acid. Since Ka values can span several orders of magnitude, a logarithmic scale known as pKa is frequently used. In this study, we conducted a predictive analysis of the acidity constant of sixteen (16) chlorophenols based on quantum-chemical molecular descriptors. The results obtained are satisfactory and promising regarding the prediction and explanation of the acidity constant for this family of molecules. A QSPR (Quantitative Structure-Property Relationship) model linking the acidity constant (pKa) to three molecular descriptors was developed. These molecular descriptors namely ionization energy (IE), standard entropy of formation (∆fS0), and the sum of the absolute values of Mulliken charges (Q) enable the explanation and prediction of the acidity constant for this family of molecules. This model exhibited highly satisfactory statistical and validation parameters. They indicate that the developed QSPR model is validated and performs well in predicting the acidity constant. It can therefore be used to effectively predict the acidity constant of other molecules within its applicability domain at a 95% confidence level.
Abstract: The acidity constant, or acid dissociation constant (Ka), is a quantitative measure of the strength of an acid in solution. It reflects the tendency of an acid to dissociate and release a proton (H⁺ or H3O+) to water. It serves as the equilibrium constant for the dissociation reaction of an acidic species within the context of acid-base reactions. ...
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