Lock‐and‐Key Principle on a Microscopic Scale: The Case of the Propylene Oxide⋅⋅⋅Ethanol Complex

Molecular recognition: The binding between propylene oxide (PO) and ethanol resembles the lock-and-key principle, with (R)-PO as a rigid lock and G−, G+, and T conformers of EtOH as different keys (see picture; C yellow, O red). Six hydrogen-bonded PO⋅⋅⋅EtOH conformers were studied using rotational spectroscopy and ab initio calculations, revealing which EtOH key fits best into the PO lock.