CCOC(=O)C1C(=O)C=C(c2ccc(NS(C)(=O)=O)cc2)CC1c1ccco1
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?