Cc1sc2ncnc(N3CCC(C(=O)Nc4nc5ccc(Cl)cc5s4)CC3)c2c1C
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?