Cc1n[nH]c(C)c1Sc1ccccc1/N=C/c1cc(Cl)cc([N+](=O)[O-])c1O
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?