COc1ccc(C(C(=O)NCC2CCCO2)N(C(=O)c2snc(C(N)=O)c2N)c2ccccc2C)cc1OC
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?