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Benzeneselenol-2D-skeletal.png Benzeneselenol-3D-vdW.png
CAS number 645-96-5 YesY
PubChem 69530
ChemSpider 62734 YesY
Jmol-3D images Image 1
Molecular formula C6H6Se
Molar mass 157.07 g/mol
Appearance colorless liquid
Density 1.479 g/cm3
Boiling point 71 to 72 °C (160 to 162 °F; 344 to 345 K) (18 mm Hg)
Solubility in water slightly
Solubility in other solvents most organic solvents
Refractive index (nD) 1.616
Dipole moment 1.1 D
R-phrases R23/25-R33-R50/53
S-phrases S20/21-S28-S45-S60-S61
Main hazards toxic
Related compounds
Related compounds Thiophenol,
Hydrogen selenide,
Diphenyl diselenide
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Benzeneselenol is the organoselenium compound with the formula C6H5SeH, often abbreviated PhSeH. It is the selenium analog of the simple aromatic alcohol phenol, and the related thiol thiophenol. This colourless, intensely malodorous compound is a useful reagent in organic synthesis.[1]

Synthesis and basic properties[edit]

Benzeneselenol is prepared via the reaction of phenylmagnesium bromide and selenium:[2]


More so than thiophenol, benzeneselenol is easily oxidized by air. The product is diphenyl diselenide as shown in this idealized equation:

4 PhSeH + O2 → 2 PhSeSePh + 2 H2O

The presence of the diselenide is indicated by a yellow coloration in most samples of PhSeH. The diselenide can be converted back to the selenol by reduction followed by acidification of the resulting PhSe.

PhSeH is approximately seven times more acidic than the related thiophenol. Both compounds dissolve in water upon the addition of base.

In organic synthesis benzeneselenol is converted to its conjugate base PhSe, a potent nucleophile.[1]


Benzeneselenol was first reported in 1888 by the reaction of benzene with selenium tetrachloride (SeCl4) in the presence of aluminium trichloride (AlCl3).[3][4]


The compound is intensely malodorous[5] and, like other organoselenium compounds, toxic.


  1. ^ a b Sonoda, N.; Ogawa, A.; Recupero, F. (2005). "Benzeneselenol". In L. Paquette. Encyclopedia of Reagents for Organic Synthesis. New York: J. Wiley & Sons. doi:10.1002/047084289X.rb018.pub2. 
  2. ^ Foster, D. G. (1944), "Selenophenol", Org. Synth. 24: 89 ; Coll. Vol. 3: 771 
  3. ^ Chabrié, M. C. (1888). "Premiers essais de synthèse de composés organiques séléniés dans la série aromatique". Bulletin de la Société Chimique de Paris 50: 133–137. 
  4. ^ Chabrié, M. C. (1890). "Sur la synthèse de quelques composés séléniés dans la série aromatique". Annales de Chimie et de Physique 6 (20): 202–286. 
  5. ^ Lowe, D. (2012-05-15). "Things I Won't Work With: Selenophenol". In the Pipeline.