O=C(COC(=O)/C=C/c1cccc(Cl)c1)Nc1ccc2[nH]c(O)nc2c1
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?