Hydrogen selenide
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| Names | |||
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| IUPAC name
Hydrogen selenide
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| Other names
Hydroselenic acid
selane selenium hydride | |||
| Identifiers | |||
3D model (JSmol)
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| ChemSpider | |||
| ECHA InfoCard | 100.029.071 | ||
| KEGG | |||
PubChem CID
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| RTECS number |
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| UN number | 2202 | ||
CompTox Dashboard (EPA)
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| Properties | |||
| H2Se | |||
| Molar mass | 80.98 g/mol | ||
| Appearance | Colorless gas | ||
| Density | 3.553 g/cm3 | ||
| Melting point | -65.73°C (207.42 K) | ||
| Boiling point | -41.25°C (231.9 K) | ||
| 0.70 g/100 mL | |||
| Solubility | soluble in CS2, phosgene | ||
| Acidity (pKa) | 3.89 | ||
| Structure | |||
| Bent | |||
| Hazards | |||
| NFPA 704 (fire diamond) | |||
| Flash point | flammable gas | ||
| Related compounds | |||
Other anions
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H2O H2S H2Te H2Po | ||
Other cations
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Na2Se Ag2Se | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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: 0.05 ppm over an 8 hour period. This compound has a very irritating smell resembling that of decayed horseradish.
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 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 + 3 H2Se
- According to the Sonoda method, H2Se is generated from the reaction of H2O and CO on Se in the presence of Et3N.
- H2Se can by synthesized by the direct reaction of H2 with elemental selenium at T > 300 °C.
- H2Se can also be prepared by means of different methods based on the in situ generation in aqueous solution of nascent hydrogen used as reducing agent, a.o., boron hydride, Marsh test and Devarda's alloy.
Elemental selenium can be recovered from H2Se through a reaction with aqueous sulfur dioxide (SO2).
- 2 H2Se + SO2 ⇌ 2 H2O + Se + S
Elemental selenium can also be directly obtained by reduction of selenite by strong reducing agent such as, e.g., ascorbic acid, hydrazine hydrochloride, or hydroxylamine hydrochloride.
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
 | This article has an unclear citation style. (September 2007) |
- 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).
- Féher, 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
- http://www.osha.gov/dts/chemicalsampling/data/CH_246700.html, OSHA GENERAL INDUSTRY PEL: 0.05 ppm, 0.2 mg/m3 ,OSHA CONSTRUCTION INDUSTRY PEL: 0.05 ppm, 0.2 mg/m3 TWA