O=C(CN(Cc1cccs1)S(=O)(=O)c1ccc(S(=O)(=O)N2CCCCC2)cc1)Nc1ccccc1
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?