COc1cc(NC(=O)C2=C(N3CCOCC3)/C(=C\c3ccc(Cl)cc3Cl)CC2)cc(OC)c1OC
An acid's negative base-10 logarithmic dissociation constant (pKa) follows directly from its underlying thermodynamics; the negative pKa is directly proportional to its standard Gibbs free energy change. What is the negative pKa value of this molecule?