Quantification of CH···π interactions: implications on how substituent effects influence aromatic interactions.

Attractive interactions between a substituted benzene ring and an α-substituted acetate group were determined experimentally by using the triptycene model system. The attractive interaction correlates well with the Hammett constants σ(m) (R(2)=0.90), but correlates much better with the acidity of the α-protons (R(2)=0.98).