O=C1C2CCCCC2C(=O)N1n1c(Cc2ccc(Cl)cc2)n[nH]c1=O
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?