Stabilizing the Exotic Carbonic Acid by Bisulfate Ion

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Environmental Chemistry

Background:

• Carbonic acid (H2CO3) is thermodynamically unstable, readily decomposing into water and carbon dioxide.
• The existence of isolated carbonic acid has been long debated due to its instability.
• Bisulfate ions are prevalent in various natural and industrial environments.

Purpose of the Study:

• To investigate the stabilization of carbonic acid (H2CO3) by bisulfate ions.
• To explore the structural, energetic, and thermal properties of the [H2CO3·HSO4]- complex.
• To provide insights into the potential existence and behavior of carbonic acid in complex chemical environments.

Main Methods:

• Density functional theory (DFT) calculations were employed to study the electronic structure and energetics.
• Molecular dynamics (MD) simulations were used to assess thermal stability at finite temperatures.
• Topological analysis and ab initio MD simulations were performed to understand bonding and reaction pathways.
• Harmonic infrared (IR) spectra were simulated for experimental validation.

Main Results:

• The bisulfate ion effectively stabilizes all three conformers of carbonic acid (H2CO3).
• The energy differences between H2CO3 isomers were reduced within the ionic complex.
• Optimized isomers of the [H2CO3·HSO4]- complex demonstrated good thermal stability and potential existence at finite temperatures.
• Hydrogen bonding interactions and simulated IR spectra were analyzed.

Conclusions:

• The bisulfate ion can stabilize the exotic carbonic acid (H2CO3) molecule, enabling its existence in ionic complexes.
• The [H2CO3·HSO4]- complex exhibits sufficient thermal stability for potential observation.
• This finding has implications for understanding the fate of carbonic acid in environments containing bisulfate ions, such as atmospheric or aqueous systems.