O=C(CN(Cc1ccc(Br)cc1)S(=O)(=O)c1ccccc1)NCc1ccccn1
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?