STRONG HYDROGEN-BONDS IN CHEMISTRY AND BIOLOGY

Hydrogen bonds are a key feature of chemical structure and reactivity. Recently there has been much interest in a special class of hydrogen bonds called ''strong'' or ''low-barrier'' and characterized by great strength, short distances, a low or vanishing barrier to hydrogen tran sfer, and distinctive features in the NMR spectrum. Although the energ y of an ordinary hydrogen bond is ca 5 kcal mol(-1), the strength of t hese hydrogen bonds may be greater than or equal to 10 kcal mol(-1). T he properties of these hydrogen bonds have been investigated by many e xperimental techniques, as well as by calculation and by correlations among those properties. Although it has been proposed that strong, sho rt, low-barrier hydrogen bonds are important in enzymatic reactions, i t is concluded that the evidence for them in small molecules and in bi omolecules is inconclusive.