O=C(Cc1ccccc1)NN1C(=O)C(Cl)C1c1cc(Br)ccc1O
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?