Hydrogen bonds, charge-assisted proton transfer

CHARGE FLUCTUATIONS OF THE HYDROGEN BOND NETWORK AND PROTON TRANSFER ASSISTED BY THE SOLVENT IN PHENOL-WATER CLUSTERS... 

Scheme 15. Contribution of two factors in strengthening of hydrogen bonds (charge and polarization) in the proton-transfer compounds charge and polarization-assisted hydrogen bonds...

The hydrogen bond in a neutral phosphoramidate is of the type polarization-assisted hydrogen bond whereas, in the proton-transfer and phosphate compounds two factors help to strength of hydrogen bond polarization-assisted and charge-assisted. 

A first example that illustrated this concept of directing a photochemical [2 + 2] dimerisation in the solid state was reported by Ito and Sheffer/ in which diamines were used to form salts from a,p unsaturated carboxylic acids. The transference of the acidic proton in carbo g lic acids by strong base leads to the molecular salts where photodimerisation occurs between two anionic moieties. For example, two cinnamate anions are positioned in parallel form suitable for a [2 -I- 2] photocycloaddition using ethylenediamine via charge-assisted hydrogen bonds 0 ). 

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