Efficient Quantum-Chemical Calculations of Acid Dissociation Constants from Free-Energy Relationships

2021 ◽  
Author(s):  
Philipp Pracht ◽  
Stefan Grimme
Keyword(s):  
Free Energy ◽  
Quantum Chemical Calculations ◽  
Quantum Chemical ◽  
Dissociation Constants ◽  
Acid Dissociation ◽  
Acid Dissociation Constants ◽  
Energy Relationships

The dissociation constants of ethylene diammonium and hexamethylene diammonium ions from 0° to 60° C

1952 ◽  
Vol 215 (1122) ◽  
pp. 416-429 ◽  
Keyword(s):  
Heat Capacity ◽  
Free Energy ◽  
Liquid Water ◽  
Dissociation Constants ◽  
Heat Content ◽  
Acid Dissociation ◽  
Ionic Charge ◽  
Acid Dissociation Constants ◽  
Heat Capacity Changes ◽  
Solvent Molecules

The two acid dissociation constants of the ethylene diammonium ion and the hexamethylene diammonium ion in water have been determined, using an e.m.f. method, from 0 to 60° C. Measurements have been made at several ionic strengths to allow thermodynamic dissociation constants to be derived, and from these the free energy, heat content, entropy and heat capacity changes accompanying the dissociations have been computed. These quantities are discussed in relation to the size of the diamine molecule, and orientation of solvent molecules by the ionic charges. It is concluded that the range over which a single ionic charge causes a significant change in the structure of liquid water is about 5 Å.

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