COC(=O)c1nc2n(n1)C(c1cccc(Cl)c1)C(C(=O)Nc1ccccc1OC)=C(C)N2
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?