O=[N+]([O-])c1cc(S(=O)(=O)Nc2cccc(C(F)(F)F)c2)ccc1-n1nnc2ccccc21
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?