Hydrogen selenide
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{{Chembox new
| Name = Hydrogen selenide
| ImageFileL1 = Hydrogen-selenide-2D-dimensions.png
| ImageSizeL1 = 130px
| ImageNameL1 = Structural diagram of the hydrogen selenide molecule
| ImageFileR1 = Hydrogen-selenide-3D-vdW.png
<!-- | ImageSizeR1 = 120px -->
| ImageNameR1 = Space-filling model of the hydrogen selenide molecule
| IUPACName = Hydrogen selenide
| OtherNames = Hydroselenic acid<br />selane<br />selenium hydride
| Section1 = {{Chembox Identifiers
| CASNo = 7783-07-5
| RTECS = X1050000
}}
| Section2 = {{Chembox Properties
| Formula = H<sub>2</sub>Se
| MolarMass = 80.9758 g/mol
| Appearance = Colorless gas.
| Density = 3.310 g/l, gas.
| Solubility = 0.70 g/100 mL
| MeltingPt = -65.73°C (207.42 K)
| BoilingPt = -41.25°C (231.9 K)
| pKa = ''3.89 (11.0 at 25C)''
}}
| Section3 = {{Chembox Structure
| MolShape = Bent
| Dipole =
}}
| Section7 = {{Chembox Hazards
| ExternalMSDS =
| MainHazards = Highly toxic, highly<br />flammable, corrosive
| NFPA-H = 4
| NFPA-R = 3
| NFPA-F = 4
| FlashPt = ?°C
| RPhrases = {{R11}}, {{R24}}, {{R26}}
| SPhrases =
}}
| Section8 = {{Chembox Related
| OtherAnions = | [[water (molecule)|H<sub>2</sub>O]]<br />[[hydrogen sulfide|H<sub>2</sub>S]]<br />[[hydrogen telluride|H<sub>2</sub>Te]]<br />[[hydrogen polonide|H<sub>2</sub>Po]]
| OtherCpds = [[selenium oxydichloride|OSeCl<sub>2</sub>]]
| OtherCations = [[silver(I) selenide|Ag<sub>2</sub>Se]]
}}
}}
'''Hydrogen selenide''' is H<sub>2</sub>Se, the simplest [[hydride]] of [[selenium]]. H<sub>2</sub>Se is a colorless, flammable gas under standard conditions. It is the most toxic selenium compound with an exposure limit: 0.3 [[parts per million|ppm]] over an 8 hour period. This compound has a very irritating smell of decayed [[horseradish]].
==Structure==
H<sub>2</sub>Se adopts a "bent" structure with a H-Se-H bond angle of 91°. Consistent with this structure, three [[Infrared|IR]]-active vibrational bands are observed: 2358, 2345, and 1034 cm<sup>−1</sup>.
==Properties==
The properties of [[Hydrogen sulfide|H<sub>2</sub>S]] and H<sub>2</sub>Se are similar, although the selenide is more acidic with p''K''<sub>a</sub> = 3.89, and the second p''K''<sub>a</sub> = 11.0 at 25°C. Reflecting its acidity, H<sub>2</sub>Se is soluble in water.
==Preparation==
H<sub>2</sub>Se can be purchased in cylinders. A number of routes to H<sub>2</sub>Se have been reported, which are suitable for both large and small scale preparations.
*H<sub>2</sub>Se is usually prepared by the action of water on Al<sub>2</sub>Se<sub>3</sub>, concomitant with formation of hydrated [[alumina]]. A related reaction involves the acid hydrolysis of FeSe.
::Al<sub>2</sub>Se<sub>3</sub> + 6 H<sub>2</sub>O {{unicode|⇌}} 2 Al(OH)<sub>3</sub> + 3 H<sub>2</sub>Se
*According to the Sonoda method, H<sub>2</sub>Se is generated from the reaction of H<sub>2</sub>O and CO on Se in the presence of Et<sub>3</sub>N.
*H<sub>2</sub>Se can by synthesized by the direct reaction of H<sub>2</sub> with elemental [[selenium]] at >350°C.
Selenium metal can be recovered from H<sub>2</sub>Se through a reaction with aqueous [[sulfur dioxide]] (SO<sub>2</sub>).
::2 H<sub>2</sub>Se + SO<sub>2</sub> {{unicode|⇌}} 2 H<sub>2</sub>O + Se + S
==Applications==
*H<sub>2</sub>Se is commonly used in the synthesis of Se-containing compounds; it adds across alkenes. Illustrative is the synthesis of selenoureas from nitriles.
[[Image:SelenoureaRxn1.PNG|350px|Selenourea reaction]]
*H<sub>2</sub>Se gas is used to [[doping (semiconductor)|dope]] semiconductors with selenium.
==References==
{{Citationstyle|date=September 2007}}
<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).
#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
==External links==
* [http://www.webelements.com/webelements/compounds/text/H/H2Se1-7783075.html WebElements page on compound's properties]
[[Category:Hydrogen compounds]]
[[Category:Selenides]]
[[de:Selenwasserstoff]]
[[it:Seleniuro di idrogeno]]
[[ja:セレン化水素]]
[[pl:Selenowodór]]
[[ru:Селеноводород]]