Hydrogen bonding in strained cyclic vicinal diols: The birth of the hydrogen bond

Certain strained cyclic vicinal diols, in which the C-O bonds are syn-periplanar or planar, form an intramolecular hydrogen bond with a (3, −1) bond critical point, whereas open-chain 1,2-diols, in which free rotation is allowed and the gauche conformation preferred, do not. A sharp donor-acceptor cut-off distance is observed.