O=C1CSc2ccc(C(=O)Nc3cccc(S(=O)(=O)Nc4ccc(Br)cc4)c3)cc2N1
An acid's negative base-10 logarithmic dissociation constant (pka) follows directly from its underlying thermodynamics; pKa is directly proportional to its standard Gibbs free energy change. What is the pka value of this molecule?