COc1cc(NC(=O)c2sc3nc(C)nc(N4CCOCC4)c3c2C)cc(OC)c1OC
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?