C[C@H](NC(=O)[C@H](Cc1ccccc1)NC(=O)c1cc2cc(Cl)ccc2n1C)C(=O)O
The negative base-10 logarithmic of dissociation constant (pka) for an acid is a direct consequence of the underlying thermodynamics of the dissociation reaction; the pKa value is directly proportional to the standard Gibbs free energy change for the reaction. What is the pka value of this molecule?