Proton Solvation Thermochemistry: A Temperature-Resolved Calibration from Ammonium Acids
Year: 2026
Type: preprint
Abstract: Chemical reactions involving protonation are ubiquitous in nature, yet their accurate description using static quantum-chemical methods remains challenging. Here, we derive a temperature-resolved aqueous free energy of H+ (G◦,aq H+ ) by combining experimental pKa data for 12 ammonium acids over 293–333 K with a high-level composite quantum-chemical protocol based on LNO-CCSD(T)/CBS energies, CPCM solvation, and conformational thermochemistry. Thermodynamic analysis gives G◦,aq H+ = −270.0 kcal/mol at 298 K, within 0.3 kcal/mol of the canonical literature value (Tissandier et al., 1998). The fitted parameters are robust under cross-validation, and validation on an independent set of 18 acids yields a mean absolute error of 0.70 pKa units.
Source: ChemRxiv
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7214144446