Acidity measurements on a heteropolyacid hydrate in acetic acid solution: A case of three hydrons ionizing independently, rather than consecutively
- Univ. of Pittsburgh, PA (United States)
Acidity measurements by {sup 13}C NMR spectroscopy with mesityl oxide (2) as indicator (the {Delta} {delta} method) have been conducted on phosphotungstic acid, H{sub 3}PW{sub 12}O{sub 40} (1) at various levels of hydration, H{sub 3}PW{sub 12}O{sub 40} {center_dot} xH{sub 2}O (1b) in concentrated solution in acetic acid. Extrapolation to infinite dilution of indicator allowed the determination of the H{sub 0} acidity function. A comparison with the strong acids, sulfuric and perchloric, indicate that even in this solvent of low basicity the three hydrons of 1 dissociate independently, rather than consecutively as considered previously. The molecule of the heteropolyacid is thus equivalent to three molecules of strong acid in solution and behaves in essence like the solid acids, having acid sites of the same strength. Comparison with other acids has to be made at triple concentrations of the latter and shows that the complex acid 1 is significantly stronger than perchloric acid, which in turn is stronger than sulfuric acid, as already known. 20 refs., 1 fig., 3 tabs.
- OSTI ID:
- 525941
- Journal Information:
- Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 1 Vol. 152; ISSN 0021-9517; ISSN JCTLA5
- Country of Publication:
- United States
- Language:
- English
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