COc1ccc(/C=C\c2onc(C)c2S(=O)(=O)N2CCC(C(=O)Nc3cccc(Cl)c3)CC2)cc1
The negative base-10 logarithmic of dissociation constant (pka) for an acid is a direct consequence of the underlying thermodynamics of the dissociation reaction; the pKa value is directly proportional to the standard Gibbs free energy change for the reaction. What is the pka value of this molecule?