O=S(=O)(c1cc(O)ccc1O)c1cccc2c(S(=O)(=O)c3cc(O)ccc3O)cccc12
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?