COc1cccc(N/C([S-])=C(/C(=O)c2ccc(C)c([N+](=O)[O-])c2)[n+]2ccccc2)c1
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?