O=C(CCc1ccccc1)Nc1nc2n(n1)C(c1ccc(Cl)cc1)CC(=O)N2
An acid's negative base-10 logarithmic dissociation constant (pKa) follows directly from its underlying thermodynamics; the negative pKa is directly proportional to its standard Gibbs free energy change. What is the negative pKa value of this molecule?