COc1ccc2c(c1)OC(c1ccc3c(c1)OCO3)C(OC(=O)Nc1cc(OC)c(OC)c(OC)c1)C2=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?