NC(=S)Nc1nc(=S)[nH]c2c1SC1=N/C(=C\c3ccco3)C(=O)N12
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?