O=C(COc1ccc([N+](=O)[O-])cc1)Nc1ccc(N2CCN(C(=O)c3ccco3)CC2)cc1
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?