C=CCCC(=O)Nc1nc2c(ccc3onc(-c4ccccc4[N+](=O)[O-])c32)s1
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?