N[C@H](C(=O)N[C@@H]1C(=O)N2C(C(=O)O)=C(Cl)CS[C@@H]12)c1ccccc1
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?