COc1cccc(NC(S)=NNC(=O)C(C)n2nc(C)c([N+](=O)[O-])c2C)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?