
TY  - JOUR
A1  - Sipos, Pal 
A1  - Bolden, Lee 
A1  - Hefter, Glenn 
A1  - May, Peter M. 
T1  - Raman Spectroscopic Study of Ion Pairing of Alkali Metal Ions with Carbonate and Sulfate in Aqueous Solutions
JF  - Australian Journal of Chemistry
JO  - Aust. J. Chem.
Y1  - 2001
VL  - 53
IS  - 10
SP  - 887
EP  - 890
KW  - Contact ion pairs; sodium ion; potassium ion; caesium ion; carbonate; sulfate; Raman spectroscopy., Na+ &#60;K+ &#60; Cs+
UR  - https://doi.org/10.1071/CH00126 
N2  - Raman spectra of carbonate and sulfate ions were recorded in aqueous solutions in the presence of large excesses of M&#8242;X (M&#8242;+ = Na+, K+ or Cs+; X&#8211; = OH&#8211; or Cl&#8211;) at 25&#176;C. The positions of the v1(A1&#8242;) symmetric stretching vibrations for both CO32&#8211; (at ~1060 cm&#8211;1) and SO42&#8211; (at ~980 cm&#8211;1) shift, by up to 10 cm&#8211;1, to lower frequencies and broaden (by up to 25%) with increasing concentrations of M&#8242;X. The shifts are slightly smaller for SO42&#8211; than for CO32&#8211; and also differ somewhat between M&#8242;OH and M&#8242;Cl solutions. The changes in the peak positions, which are indicative of contact ion pairing, show a clear dependence on the nature of the cation. However, the observed order, Na+ &#60; K+ &#60; Cs+, is directly opposite to the magnitudes of the (overall) ion-pairing constants. This anomaly is thought to be due to decreased hydration of Cs+ cf. Na+ in these highly concentrated, water-deficient solutions. Some implications of this for understanding ionic interactions in concentrated electrolyte solutions are suggested. 
ER  -

