O=C(Nc1cccc(Cl)c1)C1C2C=CC3(O2)C1C(=O)N(CCN1CCCCC1)C3C(=O)NC1CCCCC1
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?