Benzeneselenol

Chembox new
Name = Benzeneselenol
ImageFileL1 = Benzeneselenol-2D-skeletal.png ImageSizeL1 = 100 px
ImageFileR1 = Benzeneselenol-3D-vdW.png ImageSizeR1 = 125 px
IUPACName = benzeneselenol
OtherNames = Selenaphenol,
selenophenol,
phenylselenol
Section1 = Chembox Identifiers
SMILES = c1ccccc1Se
CASNo = 645-96-5
RTECS =
Section2 = Chembox Properties
Formula = C₆H₆Se
MolarMass = 157.07 g/mol
Appearance = colourless liquid
Density = 1.479 g/cm³
Solubility = slightly
Solvent = other solvents
SolubleOther = most organic solvents
MeltingPt =
BoilingPt = 71-72 °C (18 mm Hg)
Viscosity =
RefractIndex = 1.616
Section3 = Chembox Structure
Coordination =
CrystalStruct =
Dipole = 1.1 D
Section7 = Chembox Hazards
ExternalMSDS =
MainHazards = toxic
FlashPt =
RPhrases = 23/25-33-50/53
SPhrases = 20/21-28-45-60-61
Section8 = Chembox Related
OtherCpds = C₆H₅SH,
H₂Se,
diphenyl diselenide

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

ynthesis and basic properties

PhSeH is prepared via a Grignard reagent: [OrgSynth | author = Foster, D. G. | title = Selenophenol | collvol = 3 | collvolpages = 771 | year = 1955 | prep = cv3p0771] :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 + H₂OThe 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. [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.]

History

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

References