COc1cc(C(=O)NC(=S)Nc2cccc(-c3cc4ccccc4oc3=O)c2)cc(OC)c1OC
An acid's negative base-10 logarithmic dissociation constant (pKa) follows directly from its underlying thermodynamics; the negative pKa is directly proportional to its standard Gibbs free energy change. What is the negative pKa value of this molecule?