O=C1N/C(=N/N=C\C(O)C(O)C(O)C(O)CO)N/C1=C/c1ccc(Cl)cc1
An acid's negative base-10 logarithmic dissociation constant (pka) follows directly from its underlying thermodynamics; pKa is directly proportional to its standard Gibbs free energy change. What is the pka value of this molecule?