O=C(Nc1ccc(O)c2c(=O)cc(-c3ccccc3Cl)oc12)c1ccccc1Cl
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?