COCCn1c(C)cc(O)c(C(c2ccccc2Cl)N2CCN(c3ccccc3)CC2)c1=O
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?