O=C(Nc1sc2c(c1C(=O)NCC1CCCO1)CCC2)c1cc(=O)c2cc(Cl)ccc2o1
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?