Hydrogen selenide

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 ImageNameR1 = Space-filling model of the hydrogen selenide molecule
IUPACName = Hydrogen selenide
OtherNames = Hydroselenic acid
selane
selenium hydride
Section1 = Chembox Identifiers
CASNo = 7783-07-5
ChemSpiderID = 518
RTECS = X1050000
Section2 = Chembox Properties
Formula = H₂Se
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
flammable, corrosive
NFPA-H = 4
NFPA-R = 3
NFPA-F = 4
FlashPt = ?°C
RPhrases = R11, R24, R26
SPhrases =
Section8 = Chembox Related
OtherAnions = | H₂O
H₂S
H₂Te
H₂Po
OtherCpds = OSeCl₂
OtherCations = Ag₂Se

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.

tructure

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 p"K"_a = 3.89, and the second p"K"_a = 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 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 unicode|⇌ 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).
#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]