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IUPAC name benzeneselenol
Other names Selenaphenol,
CAS number 645-96-5
SMILES c1ccccc1Se
Molecular formula C6H6Se
Molar mass 157.07 g/mol
Appearance colourless liquid
Density 1.479 g/cm3
Boiling point

71-72 °C (18 mm Hg)

Solubility in water slightly
Solubility in other solvents most organic solvents
Refractive index (nD) 1.616
Dipole moment 1.1 D
Main hazards toxic
R-phrases 23/25-33-50/53
S-phrases 20/21-28-45-60-61
Related Compounds
Related compounds C6H5SH,
diphenyl diselenide
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

Benzeneselenol is the chemical compound with the formula C6H5SeH, often abbreviated PhSeH. This intensely malodorous liquid is a useful reagent in organic synthesis.

Synthesis and basic properties

PhSeH is prepared via a Grignard reagent:[1]

PhMgBr + Se → PhSeMgBr
PhSeMgBr + HCl → PhSeH + MgBrCl

More so that thiophenol, benzeneselenol is easily oxidized by air to give diphenyl diselenide. An idealized equation for this reaction is:

2 PhSeH + O → PhSeSePh + H2O

The presence of the diselenide is signaled 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 ca 7x stronger acid than the related thiophenol. Both compounds dissolve in water upon the addition of base.

PhSeH is renowned in organic synthesis as the precursor to its conjugate base PhSe-, a potent nucleophile.[2]


Benzeneselenol was first prepared by the reaction of benzene with SeCl4 in the presence of AlCl3.[3]


  1. ^ Foster, D. G. (1955). "Selenophenol". Org. Synth.; Coll. Vol. 3: 771. 
  2. ^ Sonoda, N.; Ogawa, A.; Recupero, F. "Benzeneselenol" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. DOI: 10.1002/047084289.
  3. ^ Chabrié, M. Camille “Premiers essays de synthèse de composés organiques séléniés dans la série aromatique” Bull. soc. chim. France, 50, 133 (1888); Ann. chim. phys., (6) 20, 229 (1890)
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Benzeneselenol". A list of authors is available in Wikipedia.
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