Hydrogen bond in ice

Of the enthalpy of sublimation of ice, 12.20 kcal/mole, about one-fifth can be attributed to ordinary van der Waals forces (as estimated from values for other substances) the remainder, 10 kcal/mole, represents the rupture of hydrogen bonds and leads to the value 5 kcal/mole for the energy of the O—H- O hydrogen bond in ice. The small value 1.44 kcal/mole of the enthalpy of fusion of ice shows that on melting only about 15 percent of the hydrogen bonds are broken. 

The 0.276-nm hydrogen bonds in ice are regarded as moderately strong. However, if one of the oxygen atoms in an O-H—O hydrogen bond carries a negative charge, as in the maleate monoanion, it will be... 

The same opportunity does not exist with hydrogen bonds. The OwH Ow hydrogen bond in ice is 1.72 A, whereas in the gas-phase water dimer, it is 17 percent longer, 2.02 A. In water, the best accepted value is intermediate, 1.85 A. Corresponding OwH Ow bond energies have been reported which range from 12 to 32 kJ mole-1 depending upon the state of matter and the type of measurement [28]. 

Less direct evidence for the position of the H atom also comes from proton magnetic resonance studies and from values of residual entropy. The positions of the protons in the H2O molecules in gypsum have been determined indirectly from the fine structure of the n.m.r, lines they are found to lie at a distance of 0-98 A from the 0 atom along an O-H-0 bond. For n.m.r. studies of a number of hydrates see p. 564 the method has also been used to locate the H atoms in Mg(0H)2 (p. 521). Measurements of residual entropy confirm the existence of two distinct locations for the proton in hydrogen bonds in ice (p. 539), salts of the type of KH2PO4, and Na2S04.10 H2O (which has residual entropy about two-tenths that of ice). 

FIRST PRINCIPLES COMPUTATIONAL STUDY OF HYDROGEN BONDS IN ICE L... 

It was also shown that Hbcp expressed as a double exponential is proportional to the interaction potential (U(i ) = JTIbcp(J )), where/was estimated to be the force constant of the O- H hydrogen bond in ice VIII from the values of the local energy densities at the equilibrium O- -H separation [95]. 

J.C. Li (1996). J. Chem. Phys., 105, 6733-6755. Inelastic neutron scattering studies of hydrogen bonding in ices. 

Hydrogen bonding in ice produces a very open structure. Ice is less dense than water in its liquid state. 

---