COc1cccc(NC(=O)CSc2nc3c([nH]c4ccccc43)c(=O)n2-c2cccc(Cl)c2)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?