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Names | |||
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IUPAC name
Benzeneselenol
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Other names
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Identifiers | |||
3D model (
JSmol)
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ChemSpider | |||
ECHA InfoCard | 100.010.417 | ||
EC Number |
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PubChem
CID
|
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CompTox Dashboard (
EPA)
|
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Properties | |||
C6H5SeH | |||
Molar mass | 157.085 g·mol−1 | ||
Appearance | colorless liquid | ||
Odor | extremely foul yet characteristic | ||
Density | 1.479 g/cm3 | ||
Boiling point | 71 to 72 °C (160 to 162 °F; 344 to 345 K) (18 mmHg) | ||
slightly | |||
Solubility in other solvents | most organic solvents | ||
Refractive index (nD)
|
1.616 | ||
Structure | |||
1.1 D | |||
Hazards | |||
Occupational safety and health (OHS/OSH): | |||
Main hazards
|
toxic | ||
GHS labelling: | |||
Danger | |||
H301, H331, H373, H410 | |||
Related compounds | |||
Related compounds
|
|||
Except where otherwise noted, data are given for materials in their
standard state (at 25 °C [77 °F], 100 kPa).
|
Benzeneselenol, also known as selenophenol, is the organoselenium compound with the chemical formula C6 H5 SeH, often abbreviated PhSeH. It is the selenium analog of phenol. This colourless, malodorous compound is a reagent in organic synthesis. [1]
Benzeneselenol is prepared by the reaction of phenylmagnesium bromide and selenium: [2]
Since benzeneselenol does not have a long shelf life, it is often generated in situ. A common method is by reduction of diphenyldiselenide. A further reason for this conversion is that often, it is the anion that is sought. [1]
More so than thiophenol, benzeneselenol is easily oxidized by air. The facility of this reaction reflects the weakness of the Se-H bond, bond dissociation energy of which is estimated to be between 67 and 74 kcal/mol. [1] In contrast, the S-H BDE for thiophenol is near 80 kcal/mol. [3] The product is diphenyl diselenide as shown in this idealized equation:
The presence of the diselenide in benzeneselenol is indicated by a yellow coloration. The diselenide can be converted back to the selenol by reduction followed by acidification of the resulting PhSe−.
PhSeH is acidic with a pKa of 5.9. Thus at neutral pH, it is mostly ionized:
It is approximately seven times more acidic than the related thiophenol. Both compounds dissolve in water upon the addition of base. The conjugate base is 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). [4] [5]
The compound is intensely malodorous [6] and, like other organoselenium compounds, toxic.
| |||
Names | |||
---|---|---|---|
IUPAC name
Benzeneselenol
| |||
Other names
| |||
Identifiers | |||
3D model (
JSmol)
|
|||
ChemSpider | |||
ECHA InfoCard | 100.010.417 | ||
EC Number |
| ||
PubChem
CID
|
|||
CompTox Dashboard (
EPA)
|
|||
| |||
| |||
Properties | |||
C6H5SeH | |||
Molar mass | 157.085 g·mol−1 | ||
Appearance | colorless liquid | ||
Odor | extremely foul yet characteristic | ||
Density | 1.479 g/cm3 | ||
Boiling point | 71 to 72 °C (160 to 162 °F; 344 to 345 K) (18 mmHg) | ||
slightly | |||
Solubility in other solvents | most organic solvents | ||
Refractive index (nD)
|
1.616 | ||
Structure | |||
1.1 D | |||
Hazards | |||
Occupational safety and health (OHS/OSH): | |||
Main hazards
|
toxic | ||
GHS labelling: | |||
Danger | |||
H301, H331, H373, H410 | |||
Related compounds | |||
Related compounds
|
|||
Except where otherwise noted, data are given for materials in their
standard state (at 25 °C [77 °F], 100 kPa).
|
Benzeneselenol, also known as selenophenol, is the organoselenium compound with the chemical formula C6 H5 SeH, often abbreviated PhSeH. It is the selenium analog of phenol. This colourless, malodorous compound is a reagent in organic synthesis. [1]
Benzeneselenol is prepared by the reaction of phenylmagnesium bromide and selenium: [2]
Since benzeneselenol does not have a long shelf life, it is often generated in situ. A common method is by reduction of diphenyldiselenide. A further reason for this conversion is that often, it is the anion that is sought. [1]
More so than thiophenol, benzeneselenol is easily oxidized by air. The facility of this reaction reflects the weakness of the Se-H bond, bond dissociation energy of which is estimated to be between 67 and 74 kcal/mol. [1] In contrast, the S-H BDE for thiophenol is near 80 kcal/mol. [3] The product is diphenyl diselenide as shown in this idealized equation:
The presence of the diselenide in benzeneselenol is indicated by a yellow coloration. The diselenide can be converted back to the selenol by reduction followed by acidification of the resulting PhSe−.
PhSeH is acidic with a pKa of 5.9. Thus at neutral pH, it is mostly ionized:
It is approximately seven times more acidic than the related thiophenol. Both compounds dissolve in water upon the addition of base. The conjugate base is 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). [4] [5]
The compound is intensely malodorous [6] and, like other organoselenium compounds, toxic.