COc1ccc(C2C([N+](=O)[O-])=C(N)Oc3c2c(=O)oc2ccccc32)cc1
An acid's negative base-10 logarithmic dissociation constant (pKa) follows directly from its underlying thermodynamics; the negative pKa is directly proportional to its standard Gibbs free energy change. What is the negative pKa value of this molecule?