Experimental and Theoretical Studies on Acid Dissociation Constants of 4-Hydroxycoumarin

In this work, we investigated the pKa values of the 4-Hydroxycoumarin using the experimental andcomputational methods. Experimentally, we used pH metric method to measure the pKa values of 4-Hydroxycoumarin.deprotonation constant in NaNO3 aqueous solutions with different ionic strength (0 ≤ I (mol.kg-1) ≤ 2.18) at T=308.2 K.Computationally, we report on the performance of several protocols for predicting the pKa values of aqueous solution.Calculations were carried out at the B3LYP/6-31+G(d) and MP2/6-311++G(2d,2p) levels of theory combined withCPCM model with a mean absolute deviation less than 0.7 pKa units. By comparing the calculated pKa’s for 4-hydroxycoumarin drug from various methods to their experimental values, it was found an optimal combination ofmethods for gas and solution phase energies.