O=C1CCc2cc(S(=O)(=O)NCCC(=O)NC3CCN(Cc4ccccc4)CC3)ccc2N1
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?