O=C(NC(c1ccccc1)c1ccccc1)c1nc[nH]c1C(=O)N[C@@H](Cc1ccccc1)C(=O)OCc1ccccc1
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?