COc1cc(C(C[N+](=O)[O-])c2c(N)n(C)c(=O)n(C)c2=O)ccc1O
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?