Nonclassical hydrogen bonds

Fig. 2 Overview on various hydrogen bonds ranging from strong to nonclassical hydrogen bonds (D = hydrogen-bonding donor A = hydrogen-bonding acceptor M = metal B = boron)...

A chiral phosphoric acid-catalyzed Petasis-Ferrier-type rearrangement of a seven-membered cyclic vinyl acetal resulted in the formation of a chiral tetrahydrofuran species. It was found that nonclassical hydrogen bonds between the catalyst and the substrate play an important role in controlling the stereoselectivity (14CS3515). 

Nonclassical Hydrogen Bonds - Interactions of Halogen Atoms with Il-Systems and Carbonyl Groups Factor Xa and Cathepsin L... 

The concept of hydrogen bonding is constantly evolving from classical hydrogen bonds to nonclassical (or nonconventional) hydrogen-bonded complexes. Here, on the basis of new experimental and theoretical data and new approaches to this problem, the nature of a proton-donor component and a proton-acceptor site is reformulated completely. In addition, experimental criteria that have been used successfully earlier for the detection of hydrogen bonds are also changed. 

Hydrogen bonds [3] can be classified as nonconventional (or nonclassical), when they are formed with the participation of nonconventional proton donors and/or unconventional proton acceptors ... 

Complexes modeUing supramolecular features such as salt interaction (37), classical intermolecular hydrogen bonds (38-40, 43), intramolecular hydrogen bonding (41 and 42) and nonclassical intermolecular hydrogen interaction (44). For bond distances, see Table 4.7 for references, see text. 

Miller-Westeroff, U., Evidence against nonclassical aromaticity in hydrogen-bonded systems. 6-Aminofulvene-2-aldimines, J. Am. Chem. Soc., 92, 4849-4855 (1970). 

Fig. 8.5. Complex-support interaction formation of classical hydrogen bonds (CFiB) and nonclassical dihydrogen bonds (DHB).

Metal—Carbon and Metal—Hydrogen Bond Dissociation Enthalpies from Classical and Nonclassical Calorimetric Studies... 

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