O=C(CSc1nc2nccnc2c(=O)n1CCc1c[nH]c2ccccc12)Nc1ccccc1
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?