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.

Influence du substituant tertiobutyl-4 sur les constantes d'acidité du cation cyclohexylammonium et de l'acide cyclohexane carboxylique dans les milieux mixtes eau–DMSO et méthanol–DMSO

1976 ◽  
Vol 54 (12) ◽  
pp. 1899-1905 ◽  
Author(s):  
John T. Edward ◽  
Patrick G. Farrell ◽  
Jitka Kirchnerova ◽  
Jean-Claude Halle ◽  
Robert Schaal
Keyword(s):  
Dissociation Constants ◽  
Potentiometric Method ◽  
Acid Dissociation ◽  
Cyclohexane Ring ◽  
Acid Dissociation Constants ◽  
Tert Butyl ◽  
Butyl Group ◽  
Tert Butyl Group ◽  
Solvent Molecules

Acid dissociation constants for the compounds 1–6 in water–DMSO and methanol–DMSO of varying composition have been determined by a potentiometric method. In all solvents the equatorial group ionized more easily, by gain or loss of a proton, than the axial group, but in the more aqueous solvents the presence of a tert-butyl group across the cyclohexane ring inhibited this ionization slightly. An explanation based on displacement of solvent molecules from the outer solvation sphere is advanced.

The thermodynamics of ionization of some fatty acids

1952 ◽  
Vol 215 (1122) ◽  
pp. 403-415 ◽  
Keyword(s):  
Fatty Acids ◽  
Heat Capacity ◽  
Acetic Acid ◽  
Dissociation Constants ◽  
Water Structure ◽  
Hydrocarbon Chain ◽  
Ionic Charge ◽  
Heat Capacity Changes ◽  
The Individual ◽  
Thermodynamics Of Ionization

The dissociation constants of the following fatty acids have been determined in water relative to acetic acid over the temperature range 0 to 60° C: propionic, n-valeric, n-hexoic, itfo-butyrie, iso-valeric, iso-hexoic, trimethylacetic, diethylacetic. Using Hamed’s data for acetic acid as standard, the individual dissociation constants have been evaluated. The available data for the fatty acids are analyzed to obtain the heats of ionization, and the entropy and heat capacity changes of ionization. These quantities are discussed in relation to the structure of the acid and the orientation of water molecules by the ions. It is conducted that the ions influence the water structure in a volume round the ionic charge of radius about 5 A, and that the effect of the ionic charge on the rigidity of the hydrocarbon chain and on the solvent structure both play an important part in determining the efatropy and heat capacity changes.

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