O=C(NCc1ccccc1)/C(=C/c1cccc([N+](=O)[O-])c1)NC(=O)c1ccco1
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?