Abstract
AbstractKinetic measurements of proton and oxygen exchange of the aquo beryllium(II) ion in concentrated solutions of beryllium(II) nitrate are reported. These measurements have been performed by means of 1H spin‐echo NMR and by 17O FT‐NMR using natural abundance 17G and europium(III) nitrate as a shift reagent for the 17O bulk water line. The combination of both methods allows one to separate the contributions from protolysis and water exchange. The data obtained for water exchange are k298ex = 1.8 · 103 sec−1 (rate constant for one water molecule), ΔH+ex = 41.5 kJ mol−1, and ΔS+ex = ‐44 JK−1 mol−1. Protolytic dissociation of the aquo beryllium(II) ion is found to be approximately one order of magnitude faster than water exchange: k298d = 8 · 104 sec−1 (rate constant for the tetra aquo beryllium(II) ion). ΔH+d = 31.2 kJ mol−1, and ΔS+d = −45 JK−1 mol−1 for beryllium concentrations up to 0.2 molal.
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