Hydrogen selenide
| Hydrogen selenide | |
|---|---|
| Hydrogen selenide | |
| General | |
| Systematic name | Hydrogen selenide |
| Other names | Hydroselenic acid selane selenium hydride |
| Molecular formula | H2Se |
| Molar mass | 80.9758 g/mol |
| Appearance | Colorless gas. |
| CAS number | |
| Properties | |
| Density and phase | 3.310 g/l, gas. |
| Solubility in water | 0.70 g/100 mL |
| Melting point | -65.73°C (207.42 K) |
| Boiling point | -41.25°C (231.9 K) |
| Acidity (pKa) | See Text |
| Structure | |
| Molecular shape | Planar. |
| Dipole moment | ? D |
| Hazards | |
| MSDS | External MSDS |
| Main hazards | Highly toxic, highly flammable, corrosive |
| NFPA 704 | Template:Nfpa |
| Flash point | ?°C |
| R/S statement | R: Template:R11, Template:R24, Template:R26 S: ? |
| RTECS number | X1050000 |
| Supplementary data page | |
| Structure and properties |
n, εr, etc. |
| Thermodynamic data |
Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Related compounds | |
| Other anions | Hydrogen fluoride hydrogen chloride hydrogen bromide hydrogen iodide |
| Other cations | ? |
| Related compounds | ? |
| Except where noted otherwise, data are given for materials in their standard state (at 25°C, 100 kPa) Infobox disclaimer and references | |
Hydrogen selenide is H2Se, the simplest hydride of selenium. H2Se is a colorless, flammable gas under standard conditions. It is the most toxic selenium compound with an exposure limit: 0.3 ppm over an 8 hour period.
Structure
H2Se adopts a "bent" structure with a H-Se-H bond angle of 91°. Consistent with this structure, three IR-active vibrational bands are observed: 2358, 2345, and 1034 cm-1.
Properties
The properties of H2S and H2Se are somewhat similar, although the selenide is more acidic with pKa = 3.89, and the second pKa = 11.0 at 25°C. Reflecting its acidity, H2Se is soluble in water.
Preparation
H2Se can be purchased in cylinders. A number of routes to H2Se have been reported, which are suitable for both large and small scale preparations.
- H2Se is usually prepared by the action of water on Al2Se3, concomitant with formation of hydrated alumina. A related reaction involves the acid hydrolysis of FeSe.
- Al2Se3 + 6 H2O ⇌ 2 Al(OH)3 + 6 H2Se
- According to the Sonoda method, H2Se is generated from the reactionof H2O and CO on Se in the presence of Et3N.
- H2Se can by synthesized by the direct reaction of H2 with elemental selenium at >350°C.
Selenium metal can be recovered from H2Se through a reaction with aqueous sulfur dioxide (SO2).
- 2 H2Se + SO2 ⇌ 2 H2O + Se + S
Applications
- H2Se is commonly used in the synthesis of Se-containing compounds; it adds across alkenes. Illustrative is the synthesis of selenoureas from nitriles.
- H2Se gas is used to dope semiconductors with selenium.
References
- Patnaik, Pradyot Handbook of Inorganic Chemicals. McGraw-Hill Handbooks New York (2003).
- V.I. Cohen, Synthesis 1:60-3 (1980).
- Greenwood, N. N., Earnshaw, A. Chemistry of the Elements Second Ed. Butterworth-Heinemann, Boston (1997).
- CRC Handbook of Chemistry and Physics Ed. 82. Chapman and Hall (2001-2002).
- Feher, F. In "Handbook of Preparative Inorganic Chemistry"; Brauer, E., Ed.; Academic: New York, 1963; 1, p 418.
- Sonoda, N.; Kondo K.; Nagano, K.; Kambe, N.; Morimoto, F. Angewandte Chemie, International Edition English 1980, vol. 19, page 308
External links
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