Kolbe–Schmitt reaction

{{Short description|Carboxylation chemical reaction}}

{{redirect|Kolbe process|the electrochemical decarboxylation/dimerization reaction|Kolbe electrolysis}}

{{Use dmy dates|date=December 2023}}

{{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 chemical reaction that proceeds by treating phenol with sodium hydroxide to form sodium phenoxide,{{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}} then heating sodium phenoxide with carbon dioxide under pressure (100 atm, 125 °C), then treating the product with sulfuric acid. The final product is an aromatic hydroxy acid which is also known as salicylic acid (the precursor to aspirin).{{cite journal

| title = Ueber Synthese der Salicylsäure

|trans-title= On the synthesis of salicylic acid

| author = Hermann Kolbe

| author-link = Adolph Wilhelm 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}} [https://web.archive.org/web/20200914175921/https://www.mjlphd.net/uploads/2/4/4/0/24404036/english_translation_of_on_the_synthesis_of_salicylic_acid_by_hermann_kolbe.pdf English translation] by Matthew Johnathan Leonard.{{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}}{{cite journal

| author = A. S. Lindsey and H. Jeskey

| title = The Kolbe-Schmitt Reaction

| year = 1957

| journal = Chem. Rev.

| volume = 57

| issue = 4

| pages = 583–620

| doi = 10.1021/cr50016a001}} (Review){{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}}

image:Kolbe-Schmitt.png

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

The methodology is also used in the industrial synthesis of 3-hydroxy-2-naphthoic acid; the regiochemistry of the carboxylation in this case is sensitive to temperature.{{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}}.