COc1cc(NS(=O)(=O)c2cc(Br)cc3c2N(C(=O)C2CC2)CC3)cc(OC)c1
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?