COc1ccccc1-c1nnc(SC(C(=O)c2c[nH]c3ccccc23)c2ccccc2)n1C
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?