COc1ccc(C2=NS(=O)(=O)N(C)C(C(=O)Nc3ccc4c(c3)OCO4)=C2)cc1OC
An acid's negative base-10 logarithmic dissociation constant (pka) follows directly from its underlying thermodynamics; pKa is directly proportional to its standard Gibbs free energy change. What is the pka value of this molecule?