C=CCNC1=C2C[C@@H](C)C[C@@H](OC)[C@H](OC(=O)CCCCN)[C@H](C)/C=C(\C)[C@@H](OC(N)=O)[C@H](OC)/C=C\C=C(/C)C(=O)NC(=CC1=O)C2=O.Cl
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?