Hydrogen selenide

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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: 0.3 ppm over an 8 hour period. This compound has a very irritating smell of decayed horseradish.

## Contents

* 1 Structure
* 2 Properties
* 3 Preparation
* 4 Applications
* 5 References
* 6 Additional Resources
* 7 External links

## Structure

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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

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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

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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 Template:Unicode 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 >350°C.

Selenium metal can be recovered from H2Se through a reaction with aqueous sulfur dioxide (SO2).

2 H2Se + SO2 Template:Unicode 2 H2O + Se + S

## Applications

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* 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

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## Additional Resources

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1. Patnaik, Pradyot Handbook of Inorganic Chemicals. McGraw-Hill Handbooks New York (2003).
2. V.I. Cohen, Synthesis 1:60-3 (1980).
3. Greenwood, N. N., Earnshaw, A. Chemistry of the Elements Second Ed. Butterworth-Heinemann, Boston (1997).
4. CRC Handbook of Chemistry and Physics Ed. 82. Chapman and Hall (2001-2002).
5. Féher, F. In "Handbook of Preparative Inorganic Chemistry"; Brauer, E., Ed.; Academic: New York, 1963; 1, p 418.
6. 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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* WebElements page on compound's properties

de:Selenwasserstoff it:Seleniuro di idrogeno

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