O=C1OCCN1C(=O)[C@H]1[C@H](c2ccccc2)C(c2cccc(Cl)c2)=NN1c1ccccc1
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?