COc1ccc(NC(=O)Cn2c(=O)n(Cc3ccco3)c(=O)c3sc4ccccc4c32)cc1Cl
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?