O=C1c2n[nH]c(-c3ccccc3O)c2C(c2cccc(Cl)c2)N1CC1CCCO1
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?