O=C(O)c1ccc(/C=C/c2nc3ccccc3c(=O)n2-c2ccc(Br)cc2)cc1
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?