O=C(COc1ccccc1)NC(NC(S)=Nc1ccccc1O)C(Cl)(Cl)Cl
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?