O=C(CC(=O)n1nc(-c2ccccc2)c(/N=N/c2ccccc2C(=O)O)c1-c1ccccc1)Nc1ccc(Cl)cc1
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?