O=C(C1=C(O)C(=O)N(C2CCS(=O)(=O)C2)C1c1cccc(O)c1)c1ccc(Cl)cc1
The negative base-10 logarithmic of dissociation constant (pka) for an acid is a direct consequence of the underlying thermodynamics of the dissociation reaction; the pKa value is directly proportional to the standard Gibbs free energy change for the reaction. What is the pka value of this molecule?