O=C1CS(=O)(=O)C(c2cccc(Oc3ccccc3)c2)N1c1cccc(Cl)c1Cl
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?