Hydration properties determining the reactivity of nitrite in aqueous solution

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Solution Chemistry

Background:

• The hydration properties of ions significantly influence their reactivity and reaction mechanisms.
• Solvent effects, particularly water, play a critical role in chemical processes involving ions.

Purpose of the Study:

• To investigate the structural and dynamical properties of the hydration shell of nitrite ions in aqueous solution.
• To elucidate the interaction patterns and hydrogen bonding network between nitrite ions and water molecules.

Main Methods:

• Ab initio quantum mechanical charge field molecular dynamics simulations were employed.
• Data analysis included molecular approaches, quantitative analysis of superimposed trajectories, and three-dimensional density maps.
• Power spectra analysis was used to validate the simulation method against experimental data.

Main Results:

• The study revealed an anisotropic hydration shell around the nitrite ion, with higher water density along the N-O bond direction.
• An average of 4.6 water molecules directly contact the nitrite ion, with an additional 1.5 molecules forming a hydrogen-bonding network.
• Oxygen sites exhibited stronger hydration sphere interactions, while nitrogen sites showed weaker structure and potential overestimation of water molecules.

Conclusions:

• The hydration shell of the nitrite ion is anisotropic, influencing its reactivity.
• Reactive sites are suggested to be located above and below the molecular plane, regions with lower water density.
• The Hartree-Fock method with specific basis sets is suitable for studying such aqueous ion systems.