ISSN:
1572-8927
Schlagwort(e):
Single ion free energies of transfer
;
tetraphenylarsonium tetraphenylboride assumption
;
liquid junction potential assumption
;
Ag+ ion
;
acetonitrile
;
dimethylsulfoxide
;
dimethylformamide
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Chemie und Pharmazie
Notizen:
Abstract Free energies of transfer of ions from water to mixtures of water with acetonitrile (AN), with dimethylformamide (DMF), with dimethylsulfoxide (DMSO), and with ethylene glycol have been determined using both the tetraphenylarsonium tetraphenylboride [TATB] and the negligible liquid junction potential [E j ] assumptions. By making use of ΔG tr (Ag+)[TATB]=12 kJ-mol−1 for transfer from DMSO to AN and by assuming negligible liquid junction potential in the cell $${\text{Ag|AgNO}}_{\text{3}} {\text{(0}}{\text{.01}}M{\text{),S}}\parallel {\text{Et}}_{\text{4}} {\text{NPic(0}}{\text{.1}}M{\text{),AN}}\parallel {\text{AgNO}}_{\text{3}} {\text{(0}}{\text{.01}}M{\text{),AN|Ag}}$$ single ion free energies of transfer of silver ion ΔG tr (Ag+)[E j ] from DMSO to 35 pure and mixed solvents show a standard deviation of only 2 kJ-mol−1 when compared with ΔG tr (Ag+) calculated from the TATB assumption that ΔG tr (Ph 4 As+)=ΔG tr (Ph 4 B−). The ferrocene assumption [Fc] also gives acceptable agreement with ΔG tr (Ag+)[TATB] provided that the solvents are not highly aqueous. Other cells with other junctions give less acceptable agreement between the E j and TATB assumptions. It is essential that the salt bridge is always tetraethylammonium picrate in AN, if the E j assumption is assumed. Because of the ease of making potentiometric measurements compared with the difficulty of measurements required for the TATB assumption, the negligible liquid junction potential method in the cell shown is recommended for estimating transfer free energies of single ions. The ferrocene assumption is acceptable only for non-structured aprotic solvents.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00649297
Permalink
