C=CCN1C(=O)S/C(=C/c2ccc(Sc3nc4ccccc4[nH]3)o2)C1=O
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?