Expansion of the Classic Acetylacetone Physical Chemistry Laboratory NMR Experiment: Correlation of the Enol–Keto Equilibrium Position with the Solvent Dipole Moment

An expansion of the classic NMR study of the acetylacetone enol to keto equilibrium, now widely employed in a basic form as a physical chemistry laboratory course experiment, is described. Repeating the basic experiment in a series of aprotic solvents of increasing polarity focuses the laboratory exercise on the origin of solvent-induced shifts in the equilibrium position. The results may be rigorously interpreted in the context of the Onsager–Kirkwood theory. However, a simpler theoretical explanation, more readily appreciated by undergraduate students, can be based on the interaction energy between the solute and solvent dipole moments.