COc1cc(C2C(C(=O)O)=C(COC(C)=O)Oc3cc4c(cc32)OCO4)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?