COc1cc2c(cc1OC)C1C(=O)c3c(O)cc4c(c3OC1CO2)C=CC(C)(C)O4
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?