COc1cc2c(-c3cc(Br)ccc3O)nc3c(c(C)nn3-c3ccccc3)c2cc1OC
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?