Benzeneselenol

<h2 id="synthesis">Synthesis</h2>
Benzeneselenol is prepared by the reaction of <a href="/facts/Phenylmagnesium_bromide/lx5S0Jl6">phenylmagnesium bromide</a> and <a href="/facts/Selenium/k975NApC">selenium</a>:<a class="footnote-ref" id="fnref:2" href="#fn:2">2</a>

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 <a href="/facts/Diphenyldiselenide/ca0ExdqN">diphenyldiselenide</a>. A further reason for this conversion is that often, it is the anion that is sought.<a class="footnote-ref" id="fnref:3" href="#fn:3">3</a>

<h2 id="reactions">Reactions</h2>
More so than thiophenol, benzeneselenol is easily oxidized by air. The facility of this reaction reflects the weakness of the Se-H bond, <a href="/facts/Bond_dissociation_energy/wdDb5yHN">bond dissociation energy</a> of which is estimated to be between 67 and 74 kcal/mol.<a class="footnote-ref" id="fnref:4" href="#fn:4">4</a> In contrast, the S-H BDE for thiophenol is near 80 kcal/mol.<a class="footnote-ref" id="fnref:5" href="#fn:5">5</a> The product is <a href="/facts/Diphenyl_diselenide/ca0ExdqN">diphenyl diselenide</a> as shown in this idealized equation:

4 PhSeH + O2 → 2 PhSeSePh + 2 H2O
The presence of the <a href="/facts/Diselenide/nGcl8kUK">diselenide</a> 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 <a href="/facts/PKa/t4YyRtKC">pKa</a> of 5.9. Thus at neutral <a href="/facts/PH/RnSv8D7y">pH</a>, it is mostly ionized:

PhSeH → PhSe− + H+
It is approximately seven times more acidic than the related <a href="/facts/Thiophenol/NDvtsq0E">thiophenol</a>. Both compounds dissolve in water upon the addition of base. The conjugate base is PhSe−, a potent <a href="/facts/Nucleophile/xYccoaJQ">nucleophile</a>.<a class="footnote-ref" id="fnref:6" href="#fn:6">6</a>

<h2 id="history">History</h2>
Benzeneselenol was first reported in 1888 by the reaction of <a href="/facts/Benzene/Fguue7nr">benzene</a> with <a href="/facts/Selenium_tetrachloride/K9RHwPgB">selenium tetrachloride</a> (SeCl4) in the presence of <a href="/facts/Aluminium_trichloride/xrhvSxDr">aluminium trichloride</a> (AlCl3).<a class="footnote-ref" id="fnref:7" href="#fn:7">7</a><a class="footnote-ref" id="fnref:8" href="#fn:8">8</a>

<h2 id="safety">Safety</h2>
The compound is intensely malodorous<a class="footnote-ref" id="fnref:9" href="#fn:9">9</a> and, like other organoselenium compounds, toxic.

<h2 id="references">References</h2>

<ol>
<li id="fn:1">Sonoda, Noboru; Ogawa, Akiya; Recupero, Francesco (2005). "Benzeneselenol". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rb018.pub2. ISBN 0471936235. <a href="0471936235" target="_blank">0471936235</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></li>
<li id="fn:2">Foster, D. G. (1944). "Selenophenol". Organic Syntheses. 24: 89. doi:10.15227/orgsyn.024.0089. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></li>
<li id="fn:3">Sonoda, Noboru; Ogawa, Akiya; Recupero, Francesco (2005). "Benzeneselenol". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rb018.pub2. ISBN 0471936235. <a href="0471936235" target="_blank">0471936235</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></li>
<li id="fn:4">Sonoda, Noboru; Ogawa, Akiya; Recupero, Francesco (2005). "Benzeneselenol". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rb018.pub2. ISBN 0471936235. <a href="0471936235" target="_blank">0471936235</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></li>
<li id="fn:5">Chandra, Asit K.; Nam, Pham-Cam; Nguyen, Minh Tho (2003). "The S−H Bond Dissociation Enthalpies and Acidities of Para and Meta Substituted Thiophenols: A Quantum Chemical Study". The Journal of Physical Chemistry A. 107 (43): 9182–9188. Bibcode:2003JPCA..107.9182C. doi:10.1021/jp035622w. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></li>
<li id="fn:6">Sonoda, Noboru; Ogawa, Akiya; Recupero, Francesco (2005). "Benzeneselenol". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rb018.pub2. ISBN 0471936235. <a href="0471936235" target="_blank">0471936235</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></li>
<li id="fn:7">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. <a href="http://gallica.bnf.fr/ark:/12148/bpt6k281999w/f157" target="_blank">http://gallica.bnf.fr/ark:/12148/bpt6k281999w/f157</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></li>
<li id="fn:8">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. <a href="http://gallica.bnf.fr/ark:/12148/bpt6k34890j/f200" target="_blank">http://gallica.bnf.fr/ark:/12148/bpt6k34890j/f200</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></li>
<li id="fn:9">Lowe, D. (2012-05-15). "Things I wont work with: Selenophenol". In the Pipeline. <a href="https://www.science.org/content/blog-post/things-i-won-t-work-selenophenol" target="_blank">https://www.science.org/content/blog-post/things-i-won-t-work-selenophenol</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></li>
</ol>

Benzeneselenol open-in-new

Benzeneselenol