Silicon tetrafluoride: Difference between revisions
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==Preparation== |
==Preparation== |
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SiF<sub>4</sub> is a by-product of the production of [[phosphate]] [[fertilizer]]s, resulting from the attack of [[HF]] (derived from [[fluorapatite]] protonolysis) on [[silicate]]s. In the laboratory, the compound is prepared by heating BaSiF<sub>6</sub> >300 °C, whereupon the solid releases volatile SiF<sub>4</sub>, leaving a residue of BaF<sub>2</sub>. The required BaSiF<sub>6</sub> is prepared by treating aqueous [[Dihydrogen hexafluorosilicate|fluorosilicic acid]] with [[barium chloride]].<ref>Hoffman, C. J.; Gutowsky, H. S. “Silicon Tetrafluoride” Inorganic Syntheses McGraw-Hill: New York, Volume 4, pages 145-6, 1953.</ref> The corresponding GeF<sub>4</sub> is prepared analogously, except that the thermal "cracking" requires 700 °C.<ref>Hoffman, C. J.; Gutowsky, H. S. "Germanium Tetrafluoride” Inorganic Syntheses McGraw-Hill: New York, Volume 4, pages 147-8, 1953.</ref> |
SiF<sub>4</sub> is a by-product of the production of [[phosphate]] [[fertilizer]]s, resulting from the attack of [[Hydrofluoric acid|HF]] (derived from [[fluorapatite]] protonolysis) on [[silicate]]s. In the laboratory, the compound is prepared by heating BaSiF<sub>6</sub> >300 °C, whereupon the solid releases volatile SiF<sub>4</sub>, leaving a residue of BaF<sub>2</sub>. The required BaSiF<sub>6</sub> is prepared by treating aqueous [[Dihydrogen hexafluorosilicate|fluorosilicic acid]] with [[barium chloride]].<ref>Hoffman, C. J.; Gutowsky, H. S. “Silicon Tetrafluoride” Inorganic Syntheses McGraw-Hill: New York, Volume 4, pages 145-6, 1953.</ref> The corresponding GeF<sub>4</sub> is prepared analogously, except that the thermal "cracking" requires 700 °C.<ref>Hoffman, C. J.; Gutowsky, H. S. "Germanium Tetrafluoride” Inorganic Syntheses McGraw-Hill: New York, Volume 4, pages 147-8, 1953.</ref> |
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==Uses== |
==Uses== |
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Revision as of 17:36, 12 August 2010
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| Names | |
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| IUPAC names
Tetrafluorosilane
Silicon tetrafluoride | |
| Other names
Silicon fluoride
Fluoro acid air | |
| Identifiers | |
3D model (JSmol)
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| ECHA InfoCard | 100.029.104 |
PubChem CID
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| RTECS number |
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| UN number | 1859 |
CompTox Dashboard (EPA)
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| Properties | |
| SiF4 | |
| Molar mass | 104.0791 g/mol |
| Appearance | colourless gas, fumes in moist air |
| Density | 1.66 g/cm3, solid (−95 °C) 4.69 g/L (gas) |
| Melting point | −90 °C |
| Boiling point | −86 °C |
| decomposes | |
| Structure | |
| tetrahedral | |
| 0 D | |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards
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toxic, corrosive |
| NFPA 704 (fire diamond) | |
| Related compounds | |
Other anions
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Silicon tetrachloride Silicon tetrabromide Silicon tetraiodide |
Other cations
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Carbon tetrafluoride Germanium tetrafluoride Tin tetrafluoride Lead tetrafluoride |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Silicon tetrafluoride or Tetrafluorosilane is the chemical compound with the formula SiF4. This tetrahedral molecule is notable for having a remarkably narrow liquid range (its boiling point is only 4 °C above its melting point). It was first synthesized by John Davy in 1812.[1]
Preparation
SiF4 is a by-product of the production of phosphate fertilizers, resulting from the attack of HF (derived from fluorapatite protonolysis) on silicates. In the laboratory, the compound is prepared by heating BaSiF6 >300 °C, whereupon the solid releases volatile SiF4, leaving a residue of BaF2. The required BaSiF6 is prepared by treating aqueous fluorosilicic acid with barium chloride.[2] The corresponding GeF4 is prepared analogously, except that the thermal "cracking" requires 700 °C.[3]
Uses
This volatile compound finds limited use in microelectronics and organic synthesis.[4]
Occurrence
Volcanic plumes contain significant amounts of silicon tetrafluoride, the daily production can reach several tonnes per day.[5] The silicon tetrafluoride is partly hydrolysed and forms hexafluorosilicic acid.
References
- ^ John Davy (1812). "An Account of Some Experiments on Different Combinations of Fluoric Acid". Philosophical Transactions of the Royal Society of London. 102: 352–369. doi:10.1098/rstl.1812.0020.
- ^ Hoffman, C. J.; Gutowsky, H. S. “Silicon Tetrafluoride” Inorganic Syntheses McGraw-Hill: New York, Volume 4, pages 145-6, 1953.
- ^ Hoffman, C. J.; Gutowsky, H. S. "Germanium Tetrafluoride” Inorganic Syntheses McGraw-Hill: New York, Volume 4, pages 147-8, 1953.
- ^ Shimizu, M. "Silicon(IV) Fluoride" Encyclopedia of Reagents for Organic Synthesis, 2001 John Wiley & Sons. DOI: 10.1002/047084289X.rs011
- ^ T. Mori, M. Sato, Y. Shimoike, K. Notsu (2002). "High SiF4/HF ratio detected in Satsuma-Iwojima volcano's plume by remote FT-IR observation" (PDF). Earth Planets Space. 54: 249–256.
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