O=C(Nc1nc(C2C3CC4CC(C3)CC2C4)cs1)c1cc2cc([N+](=O)[O-])ccc2oc1=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?