Isobutanol

Fusel alcohols including isobutanol are grain fermentation byproducts. Therefore, trace amounts of isobutanol may be present in many alcoholic beverages.

In 1852 Charles Adolphe Wurtz subjected such alcohols to fractional distillation and identified in some of them a butylic alcohol boiling at around 108°C.s:fr:Page:Comptes rendus hebdomadaires des séances de l’Académie des sciences, tome 035, 1852.djvu/314 Its structure was initially unclear, with some chemists believing it corresponded to butyric acid, but theoretical considerations indicated that normal butanol should have a higher boiling point, and in 1867 Emil Erlenmeyer and independently Vladimir Markovnikov determined its actual structure by proving its oxidation product to be isobutyric acid.{{Cite book |last=Roscoe |first=Henry Enfield |url=https://books.google.com/books?id=yfZRAQAAMAAJ&pg=PA576 |title=The chemistry of the hydrocarbons and their derivatives, or Organic chemistry. 1882-1892. 6 v |last2=Schorlemmer |first2=Carl |date=1888 |publisher=D. Appleton |language=en}}https://publishing.cdlib.org/ucpressebooks/view?docId=ft5g500723&chunk.id=d0e6782&toc.depth=1&toc.id=d0e6089&brand=ucpress

Isobutanol is produced by the carbonylation of propylene. Two methods are practiced industrially, hydroformylation is more common and generates a mixture of isobutyraldehyde and butyraldehyde:

:CH₃CH=CH₂ + CO + H₂ → CH₃CH₂CH₂CHO

The reaction is catalyzed by cobalt or rhodium complexes. The resulting aldehydes are hydrogenated to the alcohols, which are then separated. In Reppe carbonylation, the same products are obtained, but the hydrogenation is effected by the water-gas shift reaction.{{Ullmann | first1 = Heinz-Dieter | last1 = Hahn | first2 = Georg | last2 = Dämbkes | first3 = Norbert | last3 = Rupprich | title = Butanols|doi = 10.1002/14356007.a04_463|year=2005}}.

Propanol and methanol can be reacted to produce isobutyl alcohol via Guerbet condensation.{{cite journal

|title=Guerbet condensation of methanol with n-propanol to isobutyl alcohol over heterogeneous copper chromite/Mg–Al mixed oxides catalysts

|date=2004-09-01

|journal=Molecular Catalysis

|volume=220

|issue=2

|pages=215–220

|quote=The synthesis of isobutyl alcohol from methanol (MeOH) and n-propanol (PrOH) through the Guerbet condensation has been studied [. . .] using catalytic system of copper chromite and Mg-Al mixed oxides.

|doi=10.1016/j.molcata.2004.05.034

|first1=Carlo|last1=Carlini

|first2=Cristina|last2=Flego

|first3=Mario|last3=Marchionna

}}

{{main|Butanol fuel}}

E. coli as well as several other organisms has been genetically modified to produce C4 alcohols from glucose, including isobutanol, 1-butanol, 2-methyl-1-butanol, 3-methyl-1-butanol, and 2-phenylethanol. The host's highly active amino acid biosynthetic pathway is shifted to alcohol production. α-Ketoisovalerate, derived from valine, is prone to decarboxylation to give isobutyraldehyde, which is susceptible to reduction to the alcohol:{{Cite journal|title = Non-fermentative pathways for synthesis of branched-chain higher alcohols as biofuels|journal = Nature|pages = 86–89|volume = 451|issue = 7174|doi = 10.1038/nature06450|first1 = Shota|last1 = Atsumi|first2 = Taizo|last2 = Hanai|first3 = James C.|last3 = Liao|pmid=18172501|date=January 2008|bibcode = 2008Natur.451...86A|s2cid = 4413113}}

:(CH₃)₂CHC(O)CO₂H → (CH₃)₂CHCHO + CO₂

:(CH₃)₂CHCHO + NADH + H⁺ → (CH₃)₂CHCH₂OH + NAD⁺

The uses of isobutanol and 1-butanol are similar. They are often used interchangeably. The main applications are as varnishes and precursors to esters, which are useful solvents, e.g. isobutyl acetate. Isobutyl esters of phthalic, adipic, and related dicarboxylic acids are common plasticizers. Isobutanol is also a component of some biofuels.{{cite journal|last=Peralta-Yahya|first=Pamela P.|author2=Zhang, Fuzhong|author3=del Cardayre, Stephen B.|author4=Keasling, Jay D.|title=Microbial engineering for the production of advanced biofuels|journal=Nature|date=15 August 2012|volume=488|issue=7411|pages=320–328|doi=10.1038/nature11478|pmid=22895337|bibcode=2012Natur.488..320P|s2cid=4423203}}

Isobutanol is one of the least toxic of the butanols with an {{LD50}} of 2460 mg/kg (rat, oral).

In March 2009, the Government of Canada announced a ban on isobutanol use in cosmetics.{{citation | title = Cosmetic Chemicals Banned in Canada | journal = Chem. Eng. News | volume = 87 | issue = 11 | date = 2009-03-16 | page = 38}}.

{{Reflist|35em}}

{{Commons category|Isobutanol}}

• {{ICSC|0113|01}}
• {{PGCH|0352}}
• {{EHC|65|name=Butanols: four isomers}}
• {{HSG|009|name=Isobutanol|number=9}}

{{Alcohols}}

{{Sedatives}}

{{GABAAR PAMs}}

{{Authority control}}

Category:Alcohol solvents

Category:Primary alcohols

Category:GABAA receptor positive allosteric modulators

Category:Sedatives

Category:Hypnotics

Category:Alkanols

Category:Isobutyl compounds