View source for Chemistry:Kolbe–Schmitt reaction

{{Short description|Carboxylation chemical reaction}}
{{Reactionbox
| Name = Kolbe–Schmitt reaction
| Type = Addition reaction
| NamedAfter = {{ubl|Hermann Kolbe|Rudolf Schmitt}}
| Section3 = {{Reactionbox Identifiers
   | OrganicChemistryNamed = kolbe-schmitt-reaction
   | RSC_ontology_id = 0000182
 }}
}}
The '''Kolbe–Schmitt reaction''' or '''Kolbe process''' (named after Hermann Kolbe and Rudolf Schmitt) is a carboxylation [[Chemistry:Chemical reaction|chemical reaction]] that proceeds by treating phenol with sodium hydroxide to form [[Chemistry:Sodium phenoxide|sodium phenoxide]],<ref name=Speed>{{cite journal|author=C. S. Marvel |author2=A. L. Tanenbaum |title=γ-Phenoxypropyl Bromide|journal=Org. Synth.|year=1929|volume= 9|page=72|doi=10.15227/orgsyn.009.0072}}</ref> then heating sodium phenoxide with [[Chemistry:Carbon dioxide|carbon dioxide]] under pressure (100 [[Physics:Atmospheric pressure|atm]], 125&nbsp;°C), then treating the product with [[Chemistry:Sulfuric acid|sulfuric acid]]. The final product is an aromatic hydroxy [[Chemistry:Acid|acid]] which is also known as [[Chemistry:Salicylic acid|salicylic acid]] (the precursor to [[Chemistry:Aspirin|aspirin]]).<ref>{{cite journal
 | title = Ueber Synthese der Salicylsäure
 |trans-title= On the synthesis of salicylic acid
 | author = Hermann Kolbe
 | journal = Annalen der Chemie und Pharmacie
 | year = 1860
 | volume = 113
 | issue = 1
 | pages = 125–127
 | url = https://babel.hathitrust.org/cgi/pt?id=uiug.30112025843787;view=1up;seq=139
 | doi =  10.1002/jlac.18601130120}}</ref><ref>{{cite journal
 | title = Beitrag zur Kenntniss der Kolbe'schen Salicylsäure Synthese
 |trans-title= Contribution to [our] knowledge of Kolbe's synthesis of salicylic acid
 | author = R. Schmitt
 | journal = Journal für Praktische Chemie
 | year = 1885
 | series = 2nd series
 | volume = 31
 | issue = 1
 | pages = 397–411
 | url = https://babel.hathitrust.org/cgi/pt?id=njp.32101076786605;view=1up;seq=413
 | doi =  10.1002/prac.18850310130}}</ref><ref>{{cite journal
 | author = A. S. Lindsey and H. Jeskey
 | title = The Kolbe-Schmitt Reaction
 | year = 1957
 | journal = [[Chemistry:Chem. Rev.|Chem. Rev.]]
 | volume = 57
 | issue = 4
 | pages = 583–620
 | doi = 10.1021/cr50016a001}} (Review)</ref><ref>{{cite book|author=R. T. Morrison and R. N. Boyd|title=Organic Chemistry|edition=4th|publisher=Allyn and Bacon|year=1983|isbn=0-205-05838-8|page=[https://archive.org/details/organicchemistry04morr/page/976 976-7]|url-access=registration|url=https://archive.org/details/organicchemistry04morr/page/976}}</ref>
500px|center|The Kolbe–Schmitt reaction

By using [[Chemistry:Potassium hydroxide|potassium hydroxide]], 4-hydroxybenzoic acid is accessible, an important precursor for the versatile [[Chemistry:Paraben|paraben]] class of biocides used e.g. in personal care products.

The methodology is also used in the industrial synthesis of [[Chemistry:3-Hydroxy-2-naphthoic acid|3-hydroxy-2-naphthoic acid]];  the regiochemistry of the carboxylation in this case is sensitive to temperature.<ref name=Ullmann>{{cite encyclopedia|author=Gerald Booth|title=Naphthalene Derivatives|encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry|year=2005|publisher=Wiley-VCH|place=Weinheim|doi=10.1002/14356007.a17_009|isbn=3-527-30673-0}}.</ref>

==Reaction mechanism==
The Kolbe–Schmitt reaction proceeds via the [[Chemistry:Nucleophilic addition|nucleophilic addition]] of a phenoxide, classically [[Chemistry:Sodium phenoxide|sodium phenoxide]] (NaOC<sub>6</sub>H<sub>5</sub>), to [[Chemistry:Carbon dioxide|carbon dioxide]] to give the salicylate.
The final step is the reaction ([[Chemistry:Protonation|protonation]]) of the salicylate anion with an [[Chemistry:Acid|acid]] to form the desired '''salicylic''' acids (ortho- and para- isomers).

[[File:Kolbe-Schmitt-reaction-mechanism.png|700px|center|Kolbe–Schmitt reaction]]

== References ==
{{Reflist}}

==External links==
* [http://www.mjlphd.net/translations.html] {{Webarchive|url=https://web.archive.org/web/20201018004942/https://www.mjlphd.net/translations.html |date=18 October 2020 }} English Translation of Kolbe's seminal 1860 German article in Annalen der Chemie und Pharmacie that describes the discovery of this reaction. English title: 'On the syntheses of salicylic acid'; German title "Ueber Synthese der Salicylsäure".
* [https://commons.wikimedia.org/wiki/File:K_S_startAnimGif.gif] An animation of the reaction mechanism.

{{DEFAULTSORT:Kolbe-Schmitt reaction}}
[[Category:Addition reactions]]
[[Category:Carbon-carbon bond forming reactions]]
[[Category:Industrial processes]]
[[Category:Name reactions]]

{{Sourceattribution|Kolbe–Schmitt reaction}}