O=C(NC(c1ccccc1)c1ccc2ccccc2n1)C1CCN(Cc2ccc(Cl)c(Cl)c2)CC1
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?