O=C1COc2ccc(S(=O)(=O)CCC(=O)N3CCN(c4cccc(Cl)c4)CC3)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?