O=c1[nH]nc(-c2ccccc2)n1/N=C\CC/C=N\n1c(-c2ccccc2)n[nH]c1=O
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?