COc1cccc(C(=O)c2cn(CC(=O)Nc3cc(Cl)c(OC)cc3OC)c3nc(C)ccc3c2=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?