O=C(CC1SC(N2CCCC2)=NC1=O)Nc1ccc(C(=O)NCc2ccc(F)cc2)cc1
The negative base-10 logarithmic of dissociation constant (pka) for an acid is a direct consequence of the underlying thermodynamics of the dissociation reaction; the pKa value is directly proportional to the standard Gibbs free energy change for the reaction. What is the pka value of this molecule?