COc1cc(/C=C2/C(=O)NN(c3ccc(Cl)cc3)C2=O)ccc1OC(=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?