Thermodynamic functions of hydration of saturated uncharged organic compounds. Free energies, enthalpies and entropies at 25°C

1979 ◽  
Vol 75 (0) ◽  
pp. 1184 ◽  
Author(s):  
Sergio Cabani ◽  
Paolo Gianni
Keyword(s):  
Organic Compounds ◽  
Thermodynamic Functions ◽  
Free Energies

A group equivalents scheme for free energies of formation of organic compounds in aqueous solution

1992 ◽  
Vol 70 (4) ◽  
pp. 1042-1054 ◽  
Author(s):  
J. Peter Guthrie
Keyword(s):  
Aqueous Solution ◽  
Organic Compounds ◽  
Group Contributions ◽  
Free Energies

Group contributions have been determined allowing the calculation of free energies of formation in aqueous solution for organic compounds containing carbon, hydrogen, and oxygen. The system works well for monofunctional compounds. The available literature data for 198 compounds can be accommodated using 79 parameters with an rms deviation of 0.74 kcal/mol.

Structures, binding energies, and thermodynamic functions of NH4+, NH3•+, and their H2O complexes

1993 ◽  
Vol 71 (9) ◽  
pp. 1368-1377 ◽  
Author(s):  
David A. Armstrong ◽  
Arvi Rauk ◽  
Dake Yu
Keyword(s):  
Experimental Data ◽  
Gas Phase ◽  
Thermodynamic Functions ◽  
Hydration Shell ◽  
Binding Energies ◽  
Basis Set ◽  
Free Energies ◽  
Hydrated Complexes ◽  
Optimized Geometries ◽  
First Hydration Shell

Ab initio calculations are performed for [Formula: see text] and [Formula: see text] complexes for n = 0–5. For n = 0 and 1, the geometries of the complexes are optimized at the HF/6-31 + G* and MP2/6-31 + G* levels, and the energies are evaluated at the G2 level. For n = 2–5, the geometry optimizations and frequency calculations are carried out at the HF/6-31 + G* level, and the MP2/6-31 + G* energies are calculated at the HF optimized geometries. Basis set superposition errors are corrected by the Boys–Bernardi scheme at the HF/6-31 + G* level. The gas phase thermodynamic properties [Formula: see text] are evaluated as functions of temperature using standard statistical methods. Based on the calculated binding energies and the thermodynamic functions, the incremental changes in enthalpies and free energies, ΔHn and ΔGn, for the gas phase equilibria (H2O)n−1 M+ + H2O → (H2O)nM+ for M+ = NH4+ and NH3•+, are evaluated in comparison with the experimental data for [Formula: see text] the present results suggest conformations for the hydrated complexes observed in the experiments. The total free energy change for filling the first hydration shell is significantly more negative for NH3•+ than for NH4+.

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