COc1cc(-c2[nH]ccc2Cl)oc1C1=C2N=C3C=C2C(C(C)C)C1CCCCCCCC3.Cl
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?