Physical Nature of Hydrogen Bond

TL;DR

This paper examines the physical nature of hydrogen bonds in water, challenging conventional models, and suggests that electrostatic interactions better explain water's properties and the weak nature of hydrogen bonds.

Contribution

It proposes an electrostatic model for hydrogen bonds, providing a more consistent explanation of water's thermodynamic and spectroscopic properties than traditional models.

Findings

Electrostatic model explains dipole moment variations and vibrational shifts.

Weak hydrogen bonds contribute minimally to water dimer energy.

Hydrogen bonds are fundamentally electrostatic in nature.

Abstract

The physical nature and the correct definition of hydrogen bond (H-bond) are considered.\,\,The influence of H-bonds on the thermodynamic, kinetic, and spectroscopic properties of water is analyzed.\,\,The conventional model of H-bonds as sharply directed and saturated bridges between water molecules is incompatible with the behavior of the specific volume, evaporation heat, and self-diffusion and kinematic shear viscosity coefficients of water. On the other hand, it is shown that the variation of the dipole moment of a water molecule and the frequency shift of valence vibrations of a hydroxyl group can be totally explained in the framework of the electrostatic model of H-bond.\,\,At the same time, the temperature dependences of the heat capacity of water in the liquid and vapor states clearly testify to the existence of weak H-bonds.\,\,The analysis of a water dimer shows that the contribution of weak H-bonds to its ground state energy is approximately 4--5 times lower in comparison with the energy of electrostatic interaction between water molecules.\,\,A conclusion is made that H-bonds have the same nature in all other cases where they occur.