{{Chembox | Watchedfields = changed | verifiedrevid = 462789464 | Name = Benzeneselenol | ImageFileL1 = Benzeneselenol-2D-skeletal.png | ImageClassL1 = skin-invert | ImageFileR1 = Benzeneselenol-3D-vdW.png | ImageClassR1 = bg-transparent | IUPACName = Benzeneselenol | OtherNames = {{ubl|Phenylselenol|Selenaphenol|Selenophenol}} |Section1={{Chembox Identifiers | PubChem = 69530 | ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} | ChemSpiderID = 62734 | SMILES = [SeH]c1ccccc1 | InChI = 1/C6H6Se/c7-6-4-2-1-3-5-6/h1-5,7H | InChIKey = WDODWFPDZYSKIA-UHFFFAOYAD | StdInChI_Ref = {{stdinchicite|correct|chemspider}} | StdInChI = 1S/C6H6Se/c7-6-4-2-1-3-5-6/h1-5,7H | StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} | StdInChIKey = WDODWFPDZYSKIA-UHFFFAOYSA-N | CASNo_Ref = {{cascite|correct|??}} | CASNo = 645-96-5 | EINECS = 211-457-2 }} |Section2={{Chembox Properties | C=6|H=6|Se=1 | Appearance = colorless liquid | Odor = extremely foul yet characteristic | Density = 1.479 g/cm<sup>3</sup> | Solubility = slightly | Solvent = other solvents | SolubleOther = most organic solvents | BoilingPtC = 71 to 72 | BoilingPt_notes = (18 mmHg) | RefractIndex = 1.616 }} |Section3={{Chembox Structure | Dipole = 1.1 D }} |Section7={{Chembox Hazards | MainHazards = toxic | GHSPictograms = {{GHS06}}{{GHS08}}{{GHS09}} | GHSSignalWord = Danger | HPhrases = {{H-phrases|301|331|373|410}} | PPhrases = {{P-phrases|}} }} |Section8={{Chembox Related | OtherCompounds = {{ubl|Phenol|Thiophenol|Benzenetellurol|Hydrogen selenide|Diphenyl diselenide}} }} }}
'''Benzeneselenol''', also known as '''selenophenol''', is the organoselenium compound with the formula {{chem2|C6H6Se|auto=1}} or {{chem2|C6H5SeH}}, often abbreviated PhSeH. It is the selenium analog of phenol. This colourless, malodorous compound is a reagent in organic synthesis.<ref name=eEROS/>
==Synthesis== Benzeneselenol is prepared by the reaction of phenylmagnesium bromide and selenium:<ref>{{cite journal| last1=Foster|first1=D. G.|title= Selenophenol|year=1944|volume=24|pages=89|doi = 10.15227/orgsyn.024.0089|journal=Organic Syntheses}}</ref> :PhMgBr + Se → PhSeMgBr :PhSeMgBr + HCl → PhSeH + MgBrCl
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.<ref name=eEROS/>
==Reactions== 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.<ref name=eEROS/> In contrast, the S-H BDE for thiophenol is near 80 kcal/mol.<ref>{{cite journal |doi=10.1021/jp035622w|title=The S−H Bond Dissociation Enthalpies and Acidities of Para and Meta Substituted Thiophenols: A Quantum Chemical Study |year=2003 |last1=Chandra |first1=Asit K. |last2=Nam |first2=Pham-Cam |last3=Nguyen |first3=Minh Tho |journal=The Journal of Physical Chemistry A |volume=107 |issue=43 |pages=9182–9188 |bibcode=2003JPCA..107.9182C}}</ref> The product is diphenyl diselenide as shown in this idealized equation:
:{{chem2|4 PhSeH + O2 -> 2 PhSeSePh + 2 H2O}}
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 {{chem2|PhSe−}}.
PhSeH is acidic with a p''K''<sub>a</sub> of 5.9. Thus at neutral pH, it is mostly ionized:
:{{chem2|PhSeH → PhSe− + H+}}
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 {{chem2|PhSe−}}, a potent nucleophile.<ref name=eEROS>{{Cite book |doi = 10.1002/047084289X.rb018.pub2 |chapter = Benzeneselenol |title = Encyclopedia of Reagents for Organic Synthesis |year = 2005 |last1 = Sonoda |first1 = Noboru |last2 = Ogawa |first2 = Akiya |last3 = Recupero |first3 = Francesco |isbn = 0471936235}}</ref>
==History== Benzeneselenol was first reported in 1888 by the reaction of benzene with selenium tetrachloride ({{chem2|SeCl4}}) in the presence of aluminium trichloride ({{chem2|AlCl3}}).<ref>{{cite journal | author = Chabrié, M. C. | title = Premiers essais de synthèse de composés organiques séléniés dans la série aromatique | journal = Bulletin de la Société Chimique de Paris | year = 1888 | volume = 50 | pages = 133–137 | url = http://gallica.bnf.fr/ark:/12148/bpt6k281999w/f157}}</ref><ref>{{cite journal | author = Chabrié, M. C. | title = Sur la synthèse de quelques composés séléniés dans la série aromatique| journal = Annales de Chimie et de Physique | year = 1890 | volume = 6 | issue = 20 | pages = 202–286 | url = http://gallica.bnf.fr/ark:/12148/bpt6k34890j/f200}}</ref>
==Safety== The compound is intensely malodorous<ref name="pipeline">{{cite web | author = Lowe, D. | url = https://www.science.org/content/blog-post/things-i-won-t-work-selenophenol | work = In the Pipeline | title = Things I wont work with: Selenophenol | date = 2012-05-15}}</ref> and, like other organoselenium compounds, toxic.
==References== {{reflist}}
Category:Selenols Category:Phenyl compounds Category:Foul-smelling chemicals Category:Reagents for organic chemistry