N#CC1=C(c2ccccc2)CC(c2ccc(Cl)cc2)C(C(=O)c2ccccc2)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?