O=C1C(Cl)C(c2cc3cc(Br)ccc3nc2Cl)N1c1ccc(F)c(Cl)c1
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?