C=CCn1c(C)cc(C(=O)COC(=O)[C@@H](NC(=O)c2ccccc2Cl)C(C)C)c1C
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?