COc1ccc(-n2c(SCC(=O)Nc3ccc(NC(C)=O)cc3)nc3c4ccccc4nc-3c2O)cc1OC
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?