Quantitative Measurements of Edge‐to‐Face Aromatic Interactions by Using Chemical Double‐Mutant Cycles

Synthetic H-bonded zipper complexes have been used to quantify the magnitude of an edge-to-face aromatic interaction between a benzoyl group and an aniline ring. Four chemical double-mutant cycles were constructed by using a matrix of nine closely related complexes in which the aromatic rings were sequentially substituted for alkyl substituents. The stability constants and three-dimensional structures of the complexes were determined by using 1H NMR titrations in deuterochloroform at room temperature. The value of the interaction energy is similar in all cases, the average is -1.4 +/- 0.5 kJ mol(-1). The scope and limitations of the double-mutant approach are explored, and the consequences of conformational equilibria are discussed.