Potassium hydride
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| Identifiers | |
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3D model (JSmol)
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| ChemSpider | |
| ECHA InfoCard | 100.028.823 |
| EC Number |
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PubChem CID
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CompTox Dashboard (EPA)
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| Properties | |
| KH | |
| Molar mass | 40.1062 g/mol |
| Appearance | colourless crystals |
| Density | 1.43 g/cm3[1] |
| Melting point | decomposes at ~400 °C[2] |
| Structure | |
| cubic, cF8 | |
| Fm3m, No. 225 | |
| Related compounds | |
Other cations
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Lithium hydride Sodium hydride Rubidium hydride Caesium hydride |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Potassium hydride, KH, is a chemical compound of potassium and hydrogen. It is a hydride of potassium. It reacts with water according to the reaction:
- KH + H2O → KOH + H2
The reaction is so vigorous that often the hydrogen gas produced will, due to the heat of the reaction, ignite with the oxygen in the air, producing a lilac flame from the presence of potassium ions in the hydrogen fire. Potassium hydride also reacts violently with acids and ignites with oxygen, chlorine or fluorine. It is pyrophoric and requires careful handling. For this reason it is sold commercially as a slurry (~35%) in mineral oil.[1] In one study the compound was dispersed in paraffin to allow for better dispensing.[3]
Potassium hydride can be formed by direct combination of the metal and hydrogen. This reaction was discovered by Humphry Davy soon after his 1807 discovery of potassium, when he noted that the metal would vaporize in a current of hydrogen when heated just below its boiling point.[4]: p.25
Potassium hydride is a superbase (more reactive than sodium hydride), which can be used to deprotonate organic molecules. It is used in preparation of other superbases, RNHK and ROK, where R is an alkyl group. Potassium hydride is soluble in fused hydroxides and salt mixtures, but not in organic solvents.[1]
See also
References
- ^ a b c Pradyot Patnaik (1 July 2007). A Comprehensive Guide to the Hazardous Properties of Chemical Substances. John Wiley and Sons. pp. 631–. ISBN 978-0-470-13494-8. Retrieved 1 November 2011.
- ^ David Arthur Johnson; Open University (12 August 2002). Metals and chemical change. Royal Society of Chemistry. pp. 167–. ISBN 978-0-85404-665-2. Retrieved 1 November 2011.
- ^ Potassium Hydride in Paraffin: A Useful Base for Organic Synthesis Douglass F. Taber and Christopher G. Nelson J. Org. Chem.; 2006; 71(23) pp. 8973–8974 doi:10.1021/jo061420v
- ^ Humphry Davy (1808), The Bakerian Lecture on some new phenomena of chemical changes produced by electricity, particularly the decomposition of fixed alkalies, and the exhibition of the new substances which constitute their bases; and on the general nature of alkaline bodies. Philosophical Transactions of the Royal Society, volume 88, pages 1–44. In The Development of Chemistry, 1789–1914: Selected essays, edited by D. Knight, pp. 17–47.