Cc1ccc(C2(O)C[N+](c3ccccc3C)=C3SCCN32)cc1.[Br-]
An acid's negative base-10 logarithmic dissociation constant (pKa) follows directly from its underlying thermodynamics; the negative pKa is directly proportional to its standard Gibbs free energy change. What is the negative pKa value of this molecule?