COc1ccc(OC)c2sc(N(CCCN(C)C)C(=O)CCS(=O)(=O)c3ccccc3)nc12.Cl
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?