COc1cc2c(cc1O)C(c1cc(O)c(O)c(OC)c1)C(O)(C(=O)O)C(CO)C2O
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?