O=C1c2ccccc2C(=O)c2sc(Nc3ccc(Cl)c(Cl)c3)nc21
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?