Application of the Tareq Index in Quantitative Structure-Acidity Relationship Modeling of Inorganic Acids

Topological indices derived from chemical graph theory are widely used as molecular descriptors in quantitative structure-property relationship (QSPR) studies. However, many classical indices fail to adequately represent inorganic acids, as they typically ignore bond multiplicity and treat all chemical bonds equivalently. Recently, the Tareq Index (TI), a bond-weighted topological descriptor that explicitly incorporates bond multiplicity, was proposed for the structural characterization of inorganic acids [1]. While the index demonstrated promising structural sensitivity, its application within a predictive QSPR framework has not yet been explored. In this study, the Tareq Index is applied as a molecular descriptor to investigate quantitative relationships between molecular structure and acidity-related properties of inorganic acids. A dataset comprising a diverse set of binary acids and oxoacids is analyzed by correlating TI values with experimentally reported acidity measures. The performance of the Tareq Index is further evaluated through comparison with established degree-based topological indices. Correlation and regression analyses demonstrate a moderate to strong relationship between the Tareq Index and acidity, with the index explaining approximately half of the observed variance in 𝒑𝒌 𝒂 𝟏 values. These findings suggest that TI can serve as a useful and interpretable descriptor for QSPR modeling of inorganic acids and highlight its potential applicability in chemical informatics and computational chemistry.