O=C(CCS(=O)(=O)c1cc2c3c(c1)CCN3C(=O)CC2)Nc1cccc(Br)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?