COc1cc(C2c3c(-c4cc(C)cc(C)c4O)n[nH]c3C(=O)N2CCCO)cc(OC)c1OC
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?