Solvation of alkaline earth metal ions in N,N-dimethylformamide and N,N-dimethylacetamide – A volumetric and acoustic study

• In dmf and dma, the sequences of volumes of group 2 ions are: Mg2+ < Ca2+ < Sr2+ < Ba2+.
• In dma, Mg2+ is affected by steric congestion within its first coordination sphere.
• The obtained results are the consequence of ion–solvent bonding interactions.

Densities and sound velocities at temperatures (298.15, 303.15, 308.15, 313.15 and 318.15) K of magnesium(II), calcium(II) and strontium(II) trifluoromethanesulfonates (triflates), as well as barium(II) perchlorate in N,N-dimethylformamide (dmf) and N,N-dimethylacetamide (dma) have been measured over the composition range studied. From these results, apparent molar volumes and apparent molar isentropic compressibilities at infinite dilution, as well as expansibilities have been evaluated. The results have been discussed in terms of ion–solvent interactions and coordination number.

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