O=C(c1ccco1)N1CCCC(c2nc(O)c3nnn(Cc4ccc(Cl)cc4Cl)c3n2)C1
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?