C[C@]12CCC3[C@@H](CCC4c5nonc5CC[C@@]43C)C1C/C(=N/O)C2=O
An acid's negative base-10 logarithmic dissociation constant (pKa) follows directly from its underlying thermodynamics; the negative pKa is directly proportional to its standard Gibbs free energy change. What is the negative pKa value of this molecule?