O=C(C1=C(O)C(=O)N(c2ncccn2)C1c1ccc(Cl)c(Cl)c1)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?