COc1ccc(CCNC(=O)CCS(=O)(=O)c2cc3c(cc2Cl)NC(=O)CO3)cc1OC
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?