O=C(Nc1ccc2ccccc2c1)/C(=C/c1cccc(Br)c1)NC(=O)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?