Strength of hydrogen bond from HO-H to H3O+

Value 18.3 KJ/mole Range: Table - link KJ/mole
Organism Generic
Reference Markovitch O, Agmon N. Structure and energetics of the hydronium hydration shells. J Phys Chem A. 2007 Mar 29 111(12):2253-6. p.2255 table 1PubMed ID17388314
Method "[Researchers] studied the hydration shells of H3O+ at temperatures ranging from 260 to 340 K using the multi-state empirical valence-bond methodology (MS-EVB2)." "[Researchers] have run second-generation MS-EVB [ref 20] trajectories for 216 water molecules plus a single proton in a 18.64 Å-wide cube (corresponding to a density ?=1.0 g/cm3 at 300 K) with periodic boundary conditions and Ewald summation, at several temperatures (T) between 260 and 340 K. Each trajectory was first equilibrated (NVT ensemble) for about 100 ps and then run (with 0.5 fs time steps) without the thermostat (NVE ensemble) for 250 ps, saving the atomic coordinates every 25 fs. At each temperature several (3-10) such trajectories were generated (with different initial conditions), producing up to 100,000 time frames constituting the sample space for the statistics reported below. For each frame, the hydronium oxygen was identified as the one with the three closest hydrogen atoms, and its first two solvation shells were constructed by a nearest neighbor search algorithm (see Figure 1). Water molecules not forming hydrogen bonds to these shells were defined as “bulk water”."
Comments "The three water molecules coordinated to the H3O+ must therefore have extra-strong HBs. This type of HB is denoted by D0 in Figure 1: The “D” indicates that it is donated from the protonated center and the index i (here, i=0) is the solvation shell from which it is donated." "D0 is indeed the strongest HB [hydrogen bond] in protonated water. Its calculated bond enthalpy, cited in Table 1, is (fortuitously) close to the value of 18.4 kJ/mol previously suggested from a linear bond-energy/bond-length correlation. [Agmon, N. J. Chim. Phys. Phys. s Chim. Biol. 1996 , 93 , 1714 - 1736.]"
Entered by Uri M
ID 103913