C=CCN(CC=C)S(=O)(=O)c1ccc(NC(=S)NC(=O)/C=C/c2ccc(C)cc2)cc1
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?