O=C(Nc1cnc(N2CCC(N3CCCCC3)CC2)c(C(=O)O)c1)c1ccc(Br)cc1
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?