COc1cc(/C=C2\CN(C)CC3=C2N=C(S)NC3c2cc(OC)c(OC)c(OC)c2)cc(OC)c1OC.Cl
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?