Editing Butanol

{{Short description|Chemical compound family}}
'''Butanol''' (also called '''butyl alcohol''') is a four-carbon [[Alcohol (chemistry)|alcohol]] with a [[Chemical formula|formula]] of [[Carbon|C]]<sub>4</sub>[[Hydrogen|H]]<sub>9</sub>[[Hydroxy group|OH]], which occurs in five [[isomer]]ic structures (four structural isomers), from a straight-chain [[primary alcohol]] to a branched-chain tertiary alcohol;<ref>{{Cite journal | doi = 10.1038/nature06450| pmid = 18172501| title = Non-fermentative pathways for synthesis of branched-chain higher alcohols as biofuels| journal = Nature| volume = 451| issue = 7174| pages = 86–9| year = 2008| last1 = Atsumi | first1 = S. | last2 = Hanai | first2 = T. | last3 = Liao | first3 = J. C. | s2cid = 4413113}}</ref> all are a [[butyl]] or [[isobutyl]] group linked to a [[hydroxyl]] group (sometimes [[skeletal formula#Pseudoelement symbols|represented]] as '''BuOH''', '''''sec''-BuOH''', '''i-BuOH''', and '''''t''-BuOH'''). These are [[1-butanol]], two [[Stereoisomerism|stereoisomers]] of [[2-Butanol|''sec''-butyl alcohol]], [[isobutanol]] and [[Tert-Butyl alcohol|''tert''-butyl alcohol]]. Butanol is primarily used as a [[solvent]] and as an intermediate in [[chemical synthesis]], and may be used as a [[fuel]]. Biologically produced butanol is called '''biobutanol''', which may be ''n''-butanol or isobutanol.

==Isomers==
The unmodified term ''butanol'' usually refers to the [[open-chain compound|straight chain]] isomer with the alcohol [[functional group]] at the terminal carbon, which is also known as [[1-butanol]].  The straight chain isomer with the alcohol at an internal carbon is ''sec''-butyl alcohol or [[2-butanol]].  The branched isomer with the alcohol at a terminal carbon is [[isobutanol]] or 2-methyl-1-propanol, and the branched isomer with the alcohol at the internal carbon is [[Tert-Butyl alcohol|''tert''-butyl alcohol]] or 2-methyl-2-propanol.

{|class="wikitable skin-invert-image"
|-
|[[Image:1-Butanol skeletal.svg|138px]]
|[[Image:2-butanol Line-Structure.svg|93px]]
|[[Image:Isobutanol.svg|113px]]
|[[Image:Tert-butyl-alcohol-2D-skeletal.svg|100px]]
|-
|[[1-Butanol]] (''n''-butanol)
|[[2-Butanol]] (''sec''-butyl alcohol)
|[[Isobutanol]] (2-methylpropan-1-ol)
|[[Tert-Butyl alcohol|''tert''-butyl alcohol]] (2-methylpropan-2-ol)
|}

The butanol isomers have different melting and boiling points.  1-Butanol and isobutanol have limited solubility, ''sec''-butyl alcohol has substantially greater solubility, whereas ''tert''-butyl alcohol is [[miscible]] with water.  The hydroxyl group makes the molecule polar, promoting solubility in water, while the longer hydrocarbon chain mitigates the polarity and reduces solubility.

==Toxicity==
Butanol exhibits a low order of toxicity in single dose experiments with laboratory animals<ref>16 [[ECETOC]] JACC No. 41 n-Butanol (CAS No. 71-36-3), European Centre for Ecotoxicology and Toxicology of Chemicals, Brussels, December 2003, pages 3-4.</ref><ref>{{Cite web |url=http://www.dow.com/productsafety/finder/nbut.htm#HealthInfo |title=n-Butanol<!-- Bot generated title --> |access-date=2012-02-03 |archive-url=https://web.archive.org/web/20150402160140/http://www.dow.com/productsafety/finder/nbut.htm#HealthInfo |archive-date=2015-04-02 |url-status=dead }}</ref> and is considered safe enough for use in cosmetics.  Brief, repeated overexposure with the skin can result in [[Central nervous system depression|depression of the central nervous system]], as with other [[Alcohols#Simple alcohols|short-chain alcohol]]s.  Exposure may also cause severe eye irritation and moderate skin irritation.  The main dangers are from prolonged exposure to the alcohol's vapors. In extreme cases this includes suppression of the [[central nervous system]] and even death.  Under most circumstances, butanol is quickly metabolized to [[carbon dioxide]]. It has not been shown to [[genotoxicity|damage DNA]] or cause [[cancer]].

==Uses==

===Primary uses===
Butanol is used as a [[solvent]] for a wide variety of chemical and textile processes, in organic synthesis, and as a chemical intermediate. It is also used as a [[paint thinner]] and a solvent in other coating applications where a relatively slow evaporating latent solvent is preferable, as with lacquers and ambient-cured enamels. It is also used as a component of [[hydraulic fluid|hydraulic]] and [[brake fluid]]s.<ref>[http://www.chemicalland21.com/petrochemical/ISO-BUTANOL.htm Isobutanol at chemicalland21.com]</ref>

A 50% solution of butanol in water has been used since the 20th century to retard the drying of fresh plaster in [[fresco]] painting. The solution is usually sprayed on the wet plaster after the plaster has been trowelled smooth and extends the working period during which frescos can be painted up to 18 hours.<ref>{{Cite web|url=https://www.riveramural.org/diegosassistants|title=diego's assistants {{!}} Diego Rivera Mural Project|website=www.riveramural.org|access-date=2019-03-27}}</ref>

Butanol is used in the synthesis of [[2-Butoxyethanol|2-butoxyethanol]].  A major application for butanol is as a reactant with [[acrylic acid]] to produce [[butyl acrylate]], a primary ingredient of water based acrylic paint.<ref>{{cite book|title=Toxicological Profile for 2-Butoxyethanol and 2-butoxyethanol acetate|date=August 1998|publisher=U.S. Dept of Health and Human Services|author=Harris O.|display-authors=etal}}</ref>

It is also used as a base for [[perfumes]], but on its own has a highly alcoholic aroma.

[[Salt (chemistry)|Salts]] of butanol are chemical intermediates; for example, [[alkali metal]] salts of ''tert''-butanol are [[tert-butoxide|''tert''-butoxide]]s.

==Recreational use==
[[tert-amyl alcohol|2-Methyl-2-butanol]] is a central nervous system [[depressant]] with a similar effect upon ingestion to ethanol. Case reports have been documented demonstrating its potential for abuse.<ref>{{cite journal | url=https://doi.org/10.4088/PCC.22cr03292 | doi=10.4088/PCC.22cr03292 | title=Recreational 2-Methyl-2-Butanol Use | year=2022 | last1=Syed | first1=Alia N. | last2=Leo | first2=Raphael J. | journal=The Primary Care Companion for CNS Disorders | volume=24 | issue=6 | s2cid=253700629 | url-access=subscription }}</ref>

==Biobutanol==
{{Main|Butanol fuel}}
Butanol (''n''-butanol or isobutanol) is a potential [[biofuel]] ([[butanol fuel]]).<ref>{{cite journal|display-authors=etal|last1=Sampa Maiti |title=Quest for sustainable bio‐production and recovery of butanol as a promising solution to fossil fuel |journal=Energy Research |date=Dec 10, 2015 |volume=40 |issue=4 |pages=411–438 |doi=10.1002/er.3458|doi-access=free }}</ref> Butanol at 85 percent concentration can be used in cars designed for gasoline (petrol) without any change to the engine (unlike 85% ethanol), and it contains more energy for a given volume than ethanol and almost as much as gasoline, and a vehicle using butanol would return fuel consumption more comparable to gasoline than ethanol. Butanol can also be added to diesel fuel to reduce soot emissions.<ref>{{cite journal | author = Antoni, D. |author2=Zverlov, V. |author3=Schwarz, W. H. |name-list-style=amp | year = 2007 | title = Biofuels from Microbes | journal = Applied Microbiology and Biotechnology | volume = 77 |issue=1 | pages = 23–35 | doi=10.1007/s00253-007-1163-x | pmid = 17891391|s2cid=35454212 }}</ref> Photoautotrophic microorganisms, like cyanobacteria, can be engineered to produce 1-butanol indirectly from {{CO2}} and water.<ref>Liu, X., Miao, R., Lindberg, P., & Lindblad, P. (2019). Modular engineering for efficient photosynthetic biosynthesis of 1-butanol from CO 2 in cyanobacteria. Energy & Environmental Science, 12(9), 2765-2777.</ref>

==Production==
{{Main|Butanol fuel}}
Butanols are normally present in [[fusel alcohol]].

Since the 1950s, most butanol in the [[United States]] is produced commercially from [[fossil fuel]]s. The most common process starts with [[propene]] (propylene), which is put through a [[hydroformylation]] reaction to form [[butanal]], which is then reduced with [[hydrogen]] to 1-butanol and/or 2-butanol. ''tert''-butanol is derived from [[isobutane]] as a co-product of [[propylene oxide]] production.

[[File:Propen Hydroformylierung zu Butanol.svg|class=skin-invert-image|center]]
Butanol can also be produced by [[fermentation]] of [[biomass]] by bacteria. Prior to the 1950s, ''[[Clostridium acetobutylicum]]'' was used in [[industrial fermentation]] to produce ''n''-butanol.

==See also==
* [[A.B.E. process]]
* [[Algal fuel]]

==References==
*''Merck Index'', 12th Edition, '''1575'''.
{{Reflist}}

{{Alcohols}}
{{Authority control}}

[[Category:Alkanols]]
[[Category:Alcohol solvents]]
[[Category:Fatty alcohols]]
[[Category:Biotechnology products]]
[[Category:Liquid fuels]]
[[Category:Oxygenates]]