CCN1C/C(=C\c2ccc(Cl)cc2)c2[nH]c(=O)c(C#N)c(-c3ccc(Cl)cc3)c2C1
The negative base-10 logarithmic of dissociation constant (pka) for an acid is a direct consequence of the underlying thermodynamics of the dissociation reaction; the pKa value is directly proportional to the standard Gibbs free energy change for the reaction. What is the pka value of this molecule?