O=c1c2cc(S(=O)(=O)Nc3c(Cl)cccc3Cl)ccc2ncn1NS(=O)(=O)c1ccc2ccccc2c1
An acid's negative base-10 logarithmic dissociation constant (pKa) follows directly from its underlying thermodynamics; the negative pKa is directly proportional to its standard Gibbs free energy change. What is the negative pKa value of this molecule?