O=C(Nc1ccc(Cl)cn1)c1ccc(Br)c(S(=O)(=O)N2CCCCC2)c1
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?