COc1ccc2nc3cc(Cl)ccc3c(SCC(=O)Nc3ccccc3-c3ccccc3NC(=O)CSc3c4ccc(Cl)cc4nc4ccc(OC)cc34)c2c1
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?