O=C(O)c1ccccc1N/C=C1/C(=O)N(c2nccs2)C(=O)c2ccccc21
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?