O=C(Cn1c(=O)n(-c2ccccc2)c(=O)c2ccc(C(=O)NCc3ccc4c(c3)OCO4)cc21)Nc1ccc(Br)cc1F
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?