Surfing the π-clouds for Non-covalent Interactions: A comparative Study of arenes versus Alkenes

A comparative study by dynamic NMR spectroscopy using molecular balances indicates that non-covalent functional group interactions with an arene dominate over those with an alkene with a p-facial intramolecular hydrogen bond from a hydroxyl group to an arene being favoured by 1.2 kJmol-1. The strongest interaction observed in this study is with the cyano group and analysis of the series Y= Et, CH=CH2, C≡CH and C≡N is indicative of a weak long range electrostatic interaction and a correlation with the electrophilicity of the Ca atom of the Y substituent. Changes in the free energy differences of conformers show a linear dependences on the solvent hydrogen bond acceptor parameter β