Theoretical investigation of pKa values for selected Aromatic Phenolic derivatives:A Comparative study using DFT and Hartree-Fock Computational approaches

This study aims to theoretically calculate the acidity functions of a series of phenolic compounds using two computational methods, namely the Hartree–Fock (HF) method and Density Functional Theory (DFT), with the )6-31G( basis set for both methods. A comparison between the two methods was conducted by theoretically calculating the thermodynamic functions (ΔS, ΔH, and ΔG) and energy-related parameters, including the (HOMO , LUMO energies, hardness, chemical potential, and global electrophilicity index )using Gaussian 09W. The pKa values were determined through statistical analysis of the experimental pKa values of these compounds in relation to the theoretically calculated parameters. The results showed that the HF method provided the best performance, with a correlation coefficient of (R² = 0.989) between the experimental pKa values and the global electrophilicity index (ω). This was followed by the DFT method, which yielded a correlation coefficient of (R² = 0.977) between the experimental pKa values and the chemical potential (μ).