COc1ccc(OC)c(C2CC(c3c(O)nc4ccc(Cl)cc4c3-c3ccccc3)=NN2S(C)(=O)=O)c1
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?