View source for Alcohol (chemistry)

{{Short description|Organic compound with at least one hydroxyl (–OH) group}}
{{About|the class of chemical compounds|the alcohol found in alcoholic drinks|Alcohol (drug)||Alcohol (disambiguation)}}
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[[File:Alcohol.png|upright=0.8|thumb|right|[[Ball-and-stick model]] of an alcohol molecule ({{chem2|R3COH}}). The red and white balls represent the hydroxyl group ({{chem2|\sOH}}). The three "R"s stand for carbon [[substituent]]s or hydrogen atoms.<ref>{{cite journal|title=alcohols|url=http://goldbook.iupac.org/A00204.html|journal=IUPAC Gold Book|date=2014 |doi=10.1351/goldbook.A00204 |access-date=16 December 2013|doi-access=free|url-access=subscription}}</ref>]]
In [[chemistry]], an '''alcohol''' ({{etymology|ar|al-kuḥl|the [[Kohl (cosmetics)|kohl]]}})<ref name=ScienceFriday>{{Cite web |title=The Origin Of The Word 'Alcohol' |url=https://www.sciencefriday.com/articles/the-origin-of-the-word-alcohol/ |access-date=2024-09-30 |website=Science Friday |language=en-US}}</ref> is a type of [[organic compound]] that carries at least one [[hydroxyl]] ({{chem2|\sOH}}) [[functional group]] bound to a [[Saturated and unsaturated compounds|saturated]] carbon atom.<ref>{{GoldBookRef | title = Alcohols | file = A00204}}</ref><ref>{{cite book |doi=10.1002/9780470771259|title=The Hydroxyl Group |year=1971 |editor=Saul Patai|isbn=978-0-470-77125-9|series=PATAI'S Chemistry of Functional Groups }}</ref> Alcohols range from the simple, like [[methanol]] and [[ethanol]], to complex, like [[sugar alcohol]]s and [[cholesterol]]. The presence of an OH group strongly modifies the properties of [[Hydrocarbon|hydrocarbons]], conferring [[Hydrophile|hydrophilic]] (water-attracted) properties.  The OH group provides a site at which many reactions can occur.{{TOC limit|3}}

==History==
The flammable nature of the exhalations of wine was already known to ancient natural philosophers such as [[Aristotle]] (384–322 BCE), [[Theophrastus]] ({{circa|371}}–287 BCE), and [[Pliny the Elder]] (23/24–79 CE).<ref>{{cite book|last1=Berthelot|first1=Marcellin|author1-link=Marcellin Berthelot|last2=Houdas|first2=Octave V.|year=1893|title=La Chimie au Moyen Âge|volume=I–III|location=Paris|publisher=Imprimerie nationale}} vol. I, p. 137.</ref> However, this did not immediately lead to the isolation of alcohol, even despite the development of more advanced distillation techniques in second- and third-century [[Roman Egypt]].<ref>{{harvnb|Berthelot|Houdas|1893|loc=vol. I, pp. 138–139}}.</ref> An important recognition, first found in one of the writings attributed to [[Jabir ibn Hayyan|Jābir ibn Ḥayyān]] (ninth century CE), was that by [[Salt-effect distillation|adding salt]] to boiling wine, which increases the wine's [[relative volatility]], the flammability of the resulting vapors may be enhanced.<ref>{{cite book|last1=al-Hassan|first1=Ahmad Y.|author-link=Ahmad Y. al-Hassan|year=2009|chapter=Alcohol and the Distillation of Wine in Arabic Sources from the 8th Century|title=Studies in al-Kimya': Critical Issues in Latin and Arabic Alchemy and Chemistry|location=Hildesheim|publisher=Georg Olms Verlag|pages=283–298}} (same content also available on [http://www.history-science-technology.com/notes/notes7.html the author's website]).</ref> The distillation of wine is attested in Arabic works attributed to [[Al-Kindi|al-Kindī]] ({{circa|801}}–873 CE) and to [[Al-Farabi|al-Fārābī]] ({{circa|872}}–950), and in the 28th book of [[Al-Zahrawi|al-Zahrāwī]]'s (Latin: Abulcasis, 936–1013) ''Kitāb al-Taṣrīf'' (later translated into Latin as ''Liber servatoris'').<ref>{{harvnb|al-Hassan|2009}} (same content also available on [http://www.history-science-technology.com/notes/notes7.html the author's website]); cf. {{harvnb|Berthelot|Houdas|1893|loc=vol. I, pp. 141, 143}}. Sometimes, sulfur was also added to the wine (see {{harvnb|Berthelot|Houdas|1893|loc=vol. I, p. 143}}).</ref> In the twelfth century, recipes for the production of ''aqua ardens'' ("burning water", i.e., alcohol) by distilling wine with salt started to appear in a number of Latin works, and by the end of the thirteenth century, it had become a widely known substance among Western European chemists.<ref>{{cite book|last=Multhauf|first=Robert P.|author-link=Robert P. Multhauf|year=1966|title=The Origins of Chemistry|location=London|publisher=Oldbourne|isbn=978-2-88124-594-7}} pp. 204–206.</ref>

The works of [[Taddeo Alderotti]] (1223–1296) describe a method for concentrating alcohol involving repeated [[fractional distillation]] through a water-cooled still, by which an alcohol purity of 90% could be obtained.<ref>{{cite book|last1=Holmyard|first1=Eric John|author1-link=Eric John Holmyard|date=1957|title=Alchemy|location=Harmondsworth|publisher=Penguin Books|isbn=978-0-486-26298-7}} pp. 51–52.</ref> The medicinal properties of ethanol were studied by [[Arnald of Villanova]] (1240–1311 CE) and [[John of Rupescissa]] ({{circa|1310}}–1366), the latter of whom regarded it as a life-preserving substance able to prevent all diseases (the ''[[aqua vitae]]'' or "water of life", also called by John the ''[[Aether (classical element)|quintessence]]'' of wine).<ref>{{cite book|last=Principe|first=Lawrence M.|author-link=Lawrence M. Principe|year=2013|title=The Secrets of Alchemy|location=Chicago|publisher=The University of Chicago Press|isbn=978-0-226-10379-2}} pp. 69–71.</ref>

==Nomenclature==
===Etymology===
The word "alcohol" derives from the Arabic ''[[kohl (cosmetics)|kohl]]'' ({{langx|ar|الكحل|al-kuḥl}}), a powder used as an eyeliner.<ref>{{cite encyclopedia |url=https://www.etymonline.com/search?q=alcohol |title=Alcohol |access-date=17 May 2018 |dictionary=[[Etymonline]] |last=Harper |first=Douglas |author-link=Douglas Harper |publisher=MaoningTech}}</ref> The first part of the word ({{Transliteration|ar|[[al-]]}}) is the Arabic [[Article (grammar)|definite article]], equivalent to ''the'' in English. The second part of the word ({{Transliteration|ar|kuḥl}}) has several antecedents in [[Semitic languages]], ultimately deriving from the [[Akkadian language|Akkadian]] {{lang|akk|{{cuneiform|6|𒎎𒋆𒁉𒍣𒁕}}}} ({{Transliteration|akk|guḫlum}}), meaning [[stibnite]] or [[antimony]].<ref>[https://archive.org/details/akkadischefremdw00zimmuoft?view=theater#page/61 Zimmern, Heinrich (1915) Akkadische Fremdwörter als Beweis für babylonischen Kultureinfluss (in German), Leipzig: A. Edelmann, page 61]</ref>

Like its antecedents in Arabic and older languages, the term ''alcohol'' was originally used for the very fine powder produced by the [[sublimation (chemistry)|sublimation]] of the natural mineral [[stibnite]] to form [[antimony trisulfide]] {{chem2|Sb2S3}}. It was considered to be the essence or "spirit" of this mineral. It was used as an [[antiseptic]], eyeliner, and [[kohl (cosmetics)|cosmetic]]. Later the meaning of alcohol was extended to distilled substances in general, and then narrowed again to ethanol, when "spirits" was a synonym for [[Distilled beverage|hard liquor]].<ref>{{cite encyclopedia |url=http://www.vias.org/encyclopedia/Alcohol_004.html |encyclopedia=VIAS Encyclopedia |title=Etymology of the Word "Alcohol" |first=H. |last=Lohninger |date=21 December 2004 |access-date=17 May 2018}}</ref>

[[Paracelsus]] and [[Libavius]] both used the term ''alcohol'' to denote a fine powder, the latter speaking of an ''alcohol'' derived from antimony. At the same time Paracelsus uses the word for a volatile liquid; ''alcool'' or ''alcool vini'' occurs often in his writings.<ref>{{cite EB1911 |wstitle=Alcohol |volume=1 |page=525}}</ref>

[[Bartholomew Traheron]], in his 1543 translation of [[John of Vigo]], introduces the word as a term used by "barbarous" authors for "fine powder." Vigo wrote: "the barbarous auctours use alcohol, or (as I fynde it sometymes wryten) alcofoll, for moost fine poudre."<ref name="OED-2016">{{cite encyclopedia |title=alcohol, n. |dictionary=[[OED Online]] |publisher=[[Oxford University Press]] |date=15 November 2016}}</ref>

The 1657 ''Lexicon Chymicum'', by [[William Johnson (organist)|William Johnson]] glosses the word as "antimonium sive stibium."<ref>{{cite book |url=https://books.google.com/books?id=d645AAAAcAAJ |title=Lexicon Chymicum |last=Johnson |first=William |year=1652}}</ref> By extension, the word came to refer to any fluid obtained by distillation, including "alcohol of wine," the distilled essence of wine. [[Libavius]] in ''Alchymia'' (1594) refers to "{{tooltip|vini alcohol vel vinum alcalisatum|wine alcohol or alkaline wine}}". Johnson (1657) glosses ''alcohol vini'' as "{{tooltip|quando omnis superfluitas vini a vino separatur, ita ut accensum ardeat donec totum consumatur, nihilque fæcum aut phlegmatis in fundo remaneat|when all the excess of the wine is separated from the wine, so that the kindling burns until it is all consumed, and no dregs or phlegm remains at the bottom}}." The word's meaning became restricted to "spirit of wine" (the chemical known today as [[ethanol]]) in the 18th century and was extended to the class of substances so-called as "alcohols" in modern chemistry after 1850.<ref name="OED-2016"/>

The term ''ethanol'' was invented in 1892, [[blend word|blending]] "[[ethane]]" with the "-ol" ending of "alcohol", which was generalized as a [[libfix]].<ref>{{cite journal |journal=[[Proc. Chem. Soc.]] |date=8 July 1892 |page=128 |title=Contributions to an international system of nomenclature. The nomenclature of cycloids |first=Henry E. |last=Armstrong |quote=As ol is indicative of an OH derivative, there seems no reason why the simple word acid should not connote carboxyl, and why al should not connote COH; the names ethanol ethanal and ethanoic acid or simply ethane acid would then stand for the OH, COH and COOH derivatives of ethane. |doi=10.1039/PL8920800127 |volume=8 |issue=114 |url=https://books.google.com/books?id=ax1LAAAAYAAJ&pg=PA128}}</ref>

The term ''alcohol'' originally referred to the primary alcohol [[ethanol]] (ethyl alcohol), which is [[alcohol (drug)|used as a drug]] and is the [[Comparison of psychoactive alcohols in alcoholic drinks|main alcohol present in alcoholic drink]]s.
[[File:Examples of Nomenclature of Alcohols.jpg|thumb]]
The suffix ''-ol'' appears in the [[International Union of Pure and Applied Chemistry]] (IUPAC) [[IUPAC nomenclature of organic chemistry|chemical name]] of all substances where the hydroxyl group is the functional group with the highest priority. When a higher priority group is present in the compound, the prefix ''hydroxy-'' is used in its IUPAC name. The suffix ''-ol'' in non-IUPAC names (such as [[paracetamol]] or [[cholesterol]]) also typically indicates that the substance is an alcohol. However, some compounds that contain hydroxyl functional groups have ''trivial names'' that do not include the suffix ''-ol'' or the prefix ''hydroxy-'', e.g. the sugars [[glucose]] and [[sucrose]].

===Systematic names===
[[Chemical nomenclature|IUPAC nomenclature]] is used in scientific publications, and in writings where precise identification of the substance is important. In naming simple alcohols, the name of the alkane chain loses the terminal ''e'' and adds the suffix ''-ol'', ''e.g.'', as in "ethanol" from the alkane chain name "[[ethane]]".<ref name="Reusch-2007">{{cite web | author = William Reusch | work = VirtualText of Organic Chemistry | title = Alcohols | url = http://www.cem.msu.edu/~reusch/VirtualText/alcohol1.htm#alcnom | access-date = 14 September 2007 | archive-url = https://web.archive.org/web/20070919162404/http://www.cem.msu.edu/~reusch/VirtualText/alcohol1.htm#alcnom | archive-date = 19 September 2007 }}</ref> When necessary, the position of the hydroxyl group is indicated by a number between the alkane name and the ''-ol'': [[propan-1-ol]] for {{chem2|CH3CH2CH2OH}}, [[Isopropyl alcohol|propan-2-ol]] for {{chem2|CH3CH(OH)CH3}}. If a higher priority group is present (such as an [[aldehyde]], [[ketone]], or [[carboxylic acid]]), then the prefix ''hydroxy-''is used,<ref name="Reusch-2007"/> e.g., as in [[1-hydroxy-2-propanone]] ({{chem2|CH3C(O)CH2OH}}).<ref>Organic chemistry IUPAC nomenclature. [http://www.acdlabs.com/iupac/nomenclature/79/r79_202.htm Alcohols Rule C-201].</ref> Compounds having more than one hydroxy group are called [[polyol]]s. They are named using suffixes -diol, -triol, etc., following a list of the position numbers of the hydroxyl groups, as in [[Propylene glycol|propane-1,2-diol]] for CH<sub>3</sub>CH(OH)CH<sub>2</sub>OH (propylene glycol).
{| class="wikitable skin-invert-image"
|+ Example alcohols and representations
! [[Structural formula]]
! [[Skeletal formula]]
! [[Preferred IUPAC name]]
! Other systematic names
! Common names
! Degree
|- style="text-align: center"
| {{chem2|CH3\sCH2\sCH2\sOH}}
| [[File:Propan-1-ol.svg|100px]]
| [[propan-1-ol]]
| 1-propanol;<br />''n''-propyl alcohol
| propanol
| primary
|- style="text-align: center"
| [[File:Propan-2-ol displayed.svg|85px]]
| [[File:2-Propanol.svg|60px]]
| [[propan-2-ol]]
| 2-propanol
| isopropyl alcohol;<br />isopropanol
| secondary
|- style="text-align: center"
| [[File:Cyclohexanol displayed.svg|110px]]
| [[File:Cyclohexanol acsv.svg|100px]]
| [[cyclohexanol]]
| &nbsp;
| &nbsp;
| secondary
|- style="text-align: center"
| [[File:2-methylpropan-1-ol displayed.svg|100px]]
| [[File:Isobutanol.svg|100px]]
| [[2-methylpropan-1-ol]]
| 2-methyl-1-propanol
| isobutyl alcohol;<br />isobutanol
| primary
|- style="text-align: center"
| [[File:2-methylbutan-2-ol displayed.svg|100px]]
| [[File:Tert-pentyl-alcohol-2D-skeletal.svg|100px]]
| [[tert-Amyl alcohol|''tert''-amyl alcohol]]
| 2-methylbutan-2-ol;<br />2-methyl-2-butanol
| TAA
| tertiary
|}

In cases where the hydroxy group is bonded to an sp<sup>2</sup> carbon on an [[aromatic compound|aromatic ring]], the molecule is classified separately as a [[phenols|phenol]] and is named using the IUPAC rules for naming phenols.<ref>[http://www.acdlabs.com/iupac/nomenclature/79/r79_212.htm Organic Chemistry Nomenclature Rule C-203: Phenols]</ref> [[Phenols]] have distinct properties and are not classified as alcohols.

===Common names===
In other less formal contexts, an alcohol is often called with the name of the corresponding alkyl group followed by the word "alcohol", e.g., [[methyl group|methyl]] alcohol, [[ethyl group|ethyl]] alcohol. [[Propyl]] alcohol may be [[propanol|''n''-propyl alcohol]] or [[isopropyl alcohol]], depending on whether the hydroxyl group is bonded to the end or middle carbon on the straight [[propane]] chain. As described under systematic naming, if another group on the molecule takes priority, the alcohol moiety is often indicated using the "hydroxy-" prefix.<ref name="chem.uiuc">{{cite web|title=How to name organic compounds using the IUPAC rules|url=http://www.chem.uiuc.edu/GenChemReferences/nomenclature_rules.html|website=www.chem.uiuc.edu|publisher=THE DEPARTMENT OF CHEMISTRY AT THE UNIVERSITY OF ILLINOIS|access-date=14 November 2016}}</ref>

In archaic nomenclature, alcohols can be named as derivatives of methanol using "-carbinol" as the ending. For instance, {{chem2|(CH3)3COH}} can be named [[trimethylcarbinol]].

====Primary, secondary, and tertiary====
{{anchor|secondary|tertiary}}
Alcohols are then classified into primary, secondary (''sec-'', ''s-''), and tertiary (''tert-'', ''t-''), based upon the number of carbon atoms connected to the carbon atom that bears the [[hydroxyl]] [[functional group]]. The respective numeric shorthands 1°, 2°, and 3° are sometimes used in informal settings.<ref>{{cite web|last1=Reusch|first1=William|title=Nomenclature of Alcohols|url=http://chemwiki.ucdavis.edu/Organic_Chemistry/Alcohols/Nomenclature_of_Alcohols|website=chemwiki.ucdavis.edu/|date=2 October 2013|access-date=17 March 2015}}</ref> The primary alcohols have general formulas {{chem2|RCH2OH}}. The simplest primary alcohol is methanol ({{chem2|CH3OH}}), for which R = H, and the next is ethanol, for which {{chem2|1=R = CH3}}, the [[methyl group]]. Secondary alcohols are those of the form RR'CHOH, the simplest of which is 2-propanol ({{chem2|1=R = R' = CH3}}). For the tertiary alcohols, the general form is RR'R"COH. The simplest example is [[Tert-Butyl alcohol|''tert''-butanol]] (2-methylpropan-2-ol), for which each of R, R', and R" is {{chem2|CH3}}. In these shorthands, R, R', and R" represent [[substituents]], alkyl or other attached, generally organic groups.

==Examples==
{| class="wikitable"
! Type
! Formula
! [[IUPAC]] Name
! Common name
|-
| rowspan="6"|''Monohydric<br />alcohols''
| {{chem2|CH3OH}}
| [[Methanol]]
| Wood alcohol
|-
| {{chem2|C2H5OH}}
| [[Ethanol]]
| Alcohol, Rubbing alcohol 
|-
| {{chem2|C3H7OH}}
| [[Propan-2-ol]]
| Isopropyl alcohol,<br />Rubbing alcohol
|-
| {{chem2|C4H9OH}}
| [[Butan-1-ol]]
| Butanol,<br />Butyl alcohol
|-
| {{chem2|C5H11OH}}
| [[Pentan-1-ol]]
| Pentanol,<br />Amyl alcohol
|-
| {{chem2|C16H33OH}}
| Hexadecan-1-ol
| [[Cetyl alcohol]]
|-
| rowspan="7"|[[Sugar alcohol|''Polyhydric<br />alcohols<br />(sugar<br />alcohols)'']]
| {{chem2|C2H4(OH)2}}
| Ethane-1,2-diol
| [[Ethylene glycol]]
|-
| {{chem2|C3H6(OH)2}}
| Propane-1,2-diol
| [[Propylene glycol]]
|-
| {{chem2|C3H5(OH)3}}
| Propane-1,2,3-triol
| [[Glycerol]]
|-
| {{chem2|C4H6(OH)4}}
| Butane-1,2,3,4-tetraol
| [[Erythritol]],<br />[[Threitol]]
|-
| {{chem2|C5H7(OH)5}}
| Pentane-1,2,3,4,5-pentol
| [[Xylitol]]
|-
| {{chem2|C6H8(OH)6}}
| hexane-1,2,3,4,5,6-hexol
| [[Mannitol]],<br />[[Sorbitol]]
|-
| {{chem2|C7H9(OH)7}}
| Heptane-1,2,3,4,5,6,7-heptol
| [[Volemitol]]
|-
| rowspan="3"|''Unsaturated<br />[[aliphatic]] alcohols''
| {{chem2|C3H5OH}}
| Prop-2-ene-1-ol
| [[Allyl alcohol]]
|-
| {{chem2|C10H17OH}}
| 3,7-Dimethylocta-2,6-dien-1-ol
| [[Geraniol]]
|-
| {{chem2|C3H3OH}}
| Prop-2-yn-1-ol
| [[Propargyl alcohol]]
|-
| rowspan="2"|''[[Alicyclic]] alcohols''
| {{chem2|C6H6(OH)6}}
| Cyclohexane-1,2,3,4,5,6-hexol
| [[Inositol]]
|-
| {{chem2|C10H19OH}}
| 5-Methyl-2-(propan-2-yl)cyclohexan-1-ol
| [[Menthol]]
|}

==Applications==
[[File:Alcohol by Country.png|thumb|upright=0.9|Total recorded [[alcohol consumption by country|alcohol per capita consumption]] (15+) per year, in litres of pure ethanol<ref>{{cite web|url=https://www.who.int/entity/substance_abuse/publications/global_status_report_2004_overview.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.who.int/entity/substance_abuse/publications/global_status_report_2004_overview.pdf |archive-date=9 October 2022 |url-status=live |title=Global Status Report on Alcohol 2004 |access-date=28 November 2010}}</ref>]]

Alcohols have a long history of myriad uses. For simple mono-alcohols, which is the focus on this article, the following are most important industrial alcohols:<ref name="Falbe">{{Ullmann | first1 = Jürgen | last1 = Falbe | first2 = Helmut | last2 = Bahrmann | first3 = Wolfgang | last3 = Lipps | first4 = Dieter | last4 = Mayer | title = Alcohols, Aliphatic | doi = 10.1002/14356007.a01_279}}.</ref>
* methanol, mainly for the production of [[formaldehyde]] and as a [[fuel additive]]
* ethanol, mainly for alcoholic beverages, fuel additive, solvent, and to sterilize hospital instruments.<ref>{{Cite web |title=Alcohol {{!}} Definition, Formula, & Facts {{!}} Britannica |url=https://www.britannica.com/science/alcohol |access-date=2024-11-08 |website=www.britannica.com |language=en}}</ref>
* 1-propanol, 1-butanol, and isobutyl alcohol for use as a solvent and precursor to solvents
* C6–C11 alcohols used for [[plasticizer]]s, e.g. in [[polyvinylchloride]]
* fatty alcohol (C12–C18), precursors to [[detergent]]s
Methanol is the most common industrial alcohol, with about 12 million tons/y produced in 1980. The combined capacity of the other alcohols is about the same, distributed roughly equally.<ref name="Falbe"/>

==Toxicity==
With respect to acute toxicity, simple alcohols have low acute [[toxic]]ities. Doses of several milliliters are tolerated. For [[pentanol]]s, [[hexanol]]s, [[octanol]]s, and longer alcohols, {{LD50}} range from 2–5 g/kg (rats, oral). Ethanol is less acutely toxic.<ref>Ethanol toxicity</ref> All alcohols are mild skin irritants.<ref name="Falbe"/>

Methanol and ethylene glycol are more toxic than other simple alcohols. Their metabolism is affected by the presence of ethanol, which has a higher affinity for [[liver alcohol dehydrogenase]]. In this way, [[methanol]] will be excreted intact in urine.<ref name="Schep-2009">{{cite journal |vauthors=Schep LJ, Slaughter RJ, Vale JA, Beasley DM |title=A seaman with blindness and confusion |journal=[[BMJ]]|volume=339 |article-number=b3929 |date=30 September 2009|url=http://www.bmj.com/cgi/content/full/339/sep30_1/b3929|doi=10.1136/bmj.b3929|pmid=19793790|s2cid=6367081 |url-access=subscription}}</ref><ref>{{cite journal | last1 = Zimmerman | first1 = HE | last2 = Burkhart | first2 = KK | last3 = Donovan | first3 = JW | title = Ethylene glycol and methanol poisoning: diagnosis and treatment | journal = Journal of Emergency Nursing | volume = 25 | issue = 2 | pages = 116–20 | year = 1999 | pmid = 10097201 | doi = 10.1016/S0099-1767(99)70156-X }}</ref><ref>{{cite journal | last1 = Lobert | first1 = S | title = Ethanol, isopropanol, methanol, and ethylene glycol poisoning | journal = Critical Care Nurse | volume = 20 | issue = 6 | pages = 41–7 | year = 2000 | pmid = 11878258 | doi = 10.4037/ccn2000.20.6.41 }}</ref>

==Physical properties==
In general, the [[hydroxyl group]] makes alcohols [[polar molecule|polar]]. Those groups can form [[hydrogen bond]]s to one another and to most other compounds. Owing to the presence of the polar OH alcohols are more water-soluble than simple hydrocarbons. Methanol, ethanol, and propanol are [[miscible]] in water. [[1-Butanol]], with a four-carbon chain, is moderately soluble.

Because of [[hydrogen bonding]], alcohols tend to have higher boiling points than comparable [[hydrocarbon]]s and [[ether]]s. The boiling point of the alcohol ethanol is 78.29&nbsp;°C, compared to 69&nbsp;°C for the hydrocarbon [[hexane]], and 34.6&nbsp;°C for [[diethyl ether]].

==Occurrence in nature==
Alcohols occur widely in nature, as derivatives of [[glucose]] such as [[cellulose]] and [[hemicellulose]], and in [[phenols]] and their derivatives such as [[lignin]].<ref>{{cite book |doi=10.1002/14356007.a28_305 |chapter=Wood |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2000 |last1=Nimz |first1=Horst H. |last2=Schmitt |first2=Uwe |last3=Schwab |first3=Eckart |last4=Wittmann |first4=Otto |last5=Wolf |first5=Franz |isbn=978-3-527-30385-4 }}</ref> Starting from [[biomass]], 180 billion tons/y of complex carbohydrates (sugar polymers) are produced commercially (as of 2014).<ref>{{cite book |doi=10.1002/14356007.n05_n07 |chapter=Carbohydrates as Organic Raw Materials |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2010 |last1=Lichtenthaler |first1=Frieder W. |isbn=978-3-527-30673-2 }}</ref> Many other alcohols are pervasive in organisms, as manifested in other sugars such as [[fructose]] and [[sucrose]], in polyols such as [[glycerol]], and in some [[amino acid]]s such as [[serine]]. Simple alcohols like methanol, ethanol, and propanol occur in modest quantities in nature, and are industrially synthesized in large quantities for use as chemical precursors, fuels, and solvents.

==Production==
===Hydroxylation===
Many alcohols are produced by [[hydroxylation]], i.e., the installation of a hydroxy group using oxygen or a related oxidant.  Hydroxylation is the means by which the body processes many [[xenobiotic|poisons]], converting lipophilic compounds into hydrophilic derivatives that are more readily excreted.  Enzymes called [[hydroxylase]]s and [[oxidase]]s facilitate these conversions.

Many industrial alcohols, such as [[cyclohexanol]] for the production of [[nylon]], are produced by hydroxylation.

===Ziegler and oxo processes===
In the [[Ziegler process]], linear alcohols are produced from ethylene and [[triethylaluminium]] followed by oxidation and hydrolysis.<ref name="Falbe"/> An idealized synthesis of [[1-octanol]] is shown:

:{{chem2 | Al(C2H5)3 + 9 C2H4 -> Al(C8H17)3 }}
:{{chem2 | Al(C8H17)3 + 3O + 3 H2O -> 3 HOC8H17 + Al(OH)3 }}

The process generates a range of alcohols that are separated by [[distillation]].

Many higher alcohols are produced by [[hydroformylation]] of alkenes followed by hydrogenation. When applied to a [[terminal alkene]], as is common, one typically obtains a linear alcohol:<ref name="Falbe"/>

:{{chem2 | RCH\dCH2 + H2 + CO -> RCH2CH2CHO }}
:{{chem2 | RCH2CH2CHO + 3 H2 -> RCH2CH2CH2OH }}

Such processes give [[fatty alcohol]]s, which are useful for detergents.

===Hydration reactions===
Some low molecular weight alcohols of industrial importance are produced by the addition of water to alkenes. Ethanol, isopropanol, 2-butanol, and ''tert''-butanol are produced by this general method. Two implementations are employed, the direct and indirect methods. The direct method avoids the formation of stable intermediates, typically using acid catalysts. In the indirect method, the alkene is converted to the [[sulfate ester]], which is subsequently hydrolyzed. The direct [[hydration reaction|hydration]] uses [[ethylene]] ([[Ethanol#Hydration|ethylene hydration]])<ref name="Lodgsdon-1994">{{cite book |author =Lodgsdon J.E. |year=1994 |chapter=Ethanol |editor=Kroschwitz J.I. |title=Encyclopedia of Chemical Technology| edition=4th |volume=9 |page=820 |location=New York |publisher=John Wiley & Sons |isbn=978-0-471-52677-3}}</ref> or other alkenes from [[cracking (chemistry)|cracking]] of fractions of distilled [[crude oil]].

Hydration is also used industrially to produce the diol [[ethylene glycol]] from [[ethylene oxide]].

===Fermentation===
Ethanol is obtained by [[fermentation (biochemistry)|fermentation]] of [[glucose]] (which is often obtained from [[starch]]) in the presence of yeast.  Carbon dioxide is cogenerated. Like ethanol, [[n-Butanol|butanol]] can be produced by fermentation processes. ''Saccharomyces'' yeast are known to produce these higher alcohols at temperatures above {{convert|75|°F|°C|abbr=on}}. The bacterium ''[[Clostridium acetobutylicum]]'' can feed on [[cellulose]] (also an alcohol) to produce butanol on an industrial scale.<ref name="Zverlov-2006">{{cite journal|last1=Zverlov|first1=W|last2=Berezina|first2=O|last3=Velikodvorskaya|first3=GA|last4=Schwarz|first4=WH|s2cid=24074264|title=Bacterial acetone and butanol production by industrial fermentation in the Soviet Union: use of hydrolyzed agricultural waste for biorefinery.|journal=Applied Microbiology and Biotechnology|date=August 2006|volume=71|issue=5|pages=587–97|doi=10.1007/s00253-006-0445-z|pmid=16685494}}</ref>

===Substitution===
Primary [[alkyl halide]]s react with aqueous [[Sodium hydroxide|NaOH]] or [[Potassium hydroxide|KOH]] to give alcohols in [[nucleophilic aliphatic substitution]]. Secondary and especially tertiary alkyl halides will give the elimination (alkene) product instead. [[Grignard reagent]]s react with [[carbonyl]] groups to give secondary and tertiary alcohols. Related reactions are the [[Barbier reaction]] and the [[Nozaki–Hiyama–Kishi reaction]].

===Reduction===
[[Aldehydes]] or [[ketone]]s are [[redox|reduced]] with [[sodium borohydride]] or [[lithium aluminium hydride]] (after an acidic workup). Another reduction using [[aluminium isopropoxide]] is the [[Meerwein–Ponndorf–Verley reduction]]. [[Asymmetric hydrogenation|Noyori asymmetric hydrogenation]] is the asymmetric reduction of β-keto-esters.

===Hydrolysis===
[[Alkenes]] engage in an acid catalyzed [[hydration reaction]] using concentrated sulfuric acid as a catalyst that gives usually secondary or tertiary alcohols. Formation of a secondary alcohol via [[Hydration reaction#Alkenes|alkene reduction and hydration]] is shown:

:[[File:Secondary alcohol formation-diagram.svg|class=skin-invert-image|frameless|upright=1.6|Preparation of a secondary alcohol]]

The [[hydroboration-oxidation]] and [[oxymercuration-reduction]] of alkenes are more reliable in organic synthesis. Alkenes react with [[N-Bromosuccinimide|''N''-bromosuccinimide]] and water in [[halohydrin formation reaction]]. [[Amine]]s can be converted to [[diazonium salt]]s, which are then hydrolyzed.

==Reactions==<!-- This section is linked from [[Organic reaction]] -->

===Deprotonation===
With aqueous [[pKa|p''K''<sub>a</sub>]] values of around 16–19, alcohols are, in general, slightly weaker [[acid]]s than [[water]]. With strong bases such as [[sodium hydride]] or [[sodium]] they form [[Salt (chemistry)|salt]]s{{efn|Although commonly described as "salts", alkali metal alkoxides are actually better described structurally as oligomeric clusters or polymeric chains.  For instance, potassium ''tert''-butoxide consists of a cubane-like tetramer, {{chem2|[''t''\-BuOK]4}}, that persists even in polar solvents like THF.}} called ''[[alkoxide]]s'', with the general formula {{chem2|RO-M+}} (where R is an [[alkyl]] and M is a [[metal]]).
:{{chem2 | R\sOH + NaH -> R\sO-Na+ + H2 }}
:{{chem2 | 2 R\sOH + 2 Na -> 2 R\sO-Na+ + H2 }}

The acidity of alcohols is strongly affected by [[solvation]]. In the gas phase, alcohols are more acidic than in water.<ref>{{March6th|mode=cs1}}</ref> In [[DMSO]], alcohols (and water) have a p''K''<sub>a</sub> of around 29–32. As a consequence, alkoxides (and hydroxide) are powerful bases and nucleophiles (e.g., for the [[Williamson ether synthesis]]) in this solvent. In particular, {{chem2|RO-}} or {{chem2|HO-}} in DMSO can be used to generate significant equilibrium concentrations of acetylide ions through the deprotonation of alkynes (see [[Favorskii reaction]]).<ref>{{cite journal|last1=Ahmed|first1=Jasimuddin|last2=Swain|first2=Asim Kumar|last3=Das|first3=Arpan|last4=Govindarajan|first4=R.|last5=Bhunia|first5=Mrinal|last6=Mandal|first6=Swadhin K.|date=14 November 2019|title=A K-arylacetylide complex for catalytic terminal alkyne functionalization using KOtBu as a precatalyst|url=https://pubs.rsc.org/en/content/articlelanding/2019/cc/c9cc07833a|journal=Chemical Communications|language=en|volume=55|issue=92|pages=13860–13863|doi=10.1039/C9CC07833A|pmid=31670328|s2cid=204974842|issn=1364-548X|url-access=subscription}}</ref><ref>{{cite patent|number=WO1994012457A1|title=Process for preparing tertiary alkynols|gdate=1994-06-09|invent1=Babler|inventor1-first=James H.|url=https://patents.google.com/patent/WO1994012457A1/en}}</ref>

===Nucleophilic substitution===
Tertiary alcohols react with [[hydrochloric acid]] to produce tertiary [[alkyl chloride]]. Primary and secondary alcohols are converted to the corresponding chlorides using [[thionyl chloride]] and various phosphorus chloride reagents.<ref>{{cite book |doi=10.1002/9780470771259.ch11|chapter=Displacement of Hydroxyl Groups |title=The Hydroxyl Group (1971) |year=1971 |last1=Brown |first1=Geoffrey W. |series=PATai's Chemistry of Functional Groups |pages=593–639 |isbn=978-0-470-77125-9 }}</ref>
:[[File:Alcohol reaction examples.svg|class=skin-invert-image|frameless|upright=3.2|Some simple conversions of alcohols to alkyl chlorides]]

Primary and secondary alcohols, likewise, convert to [[alkyl bromide]]s using [[phosphorus tribromide]], for example:
:{{chem2 | 3 R\sOH + PBr3 -> 3 RBr + H3PO3 }}

In the [[Barton–McCombie deoxygenation]] an alcohol is deoxygenated to an [[alkane]] with [[tributyltin hydride]] or a [[organoborane|trimethylborane]]-water complex in a [[radical substitution]] reaction.

===Dehydration===
Meanwhile, the oxygen atom has [[lone pair]]s of nonbonded electrons that render it weakly [[Base (chemistry)|basic]] in the presence of strong acids such as [[sulfuric acid]]. For example, with methanol:

:[[File:Methanol acid base.svg|class=skin-invert-image|frameless|upright=2.25|Acidity & basicity of methanol]]

Upon treatment with strong acids, alcohols undergo the E1 [[elimination reaction]] to produce [[alkene]]s. The reaction, in general, obeys [[Zaytsev's rule]], which states that the most stable (usually the most substituted) alkene is formed. Tertiary alcohols are eliminated easily at just above room temperature, but primary alcohols require a higher temperature.

This is a diagram of acid catalyzed dehydration of ethanol to produce [[ethylene]]:

:[[File:DehydrationOfAlcoholWithH-.png|class=skin-invert-image|frameless|upright=2.5]]

A more controlled elimination reaction requires the formation of the [[xanthate ester]].

===Protonolysis===
Tertiary alcohols react with strong acids to generate carbocations. The reaction is related to their dehydration, e.g. [[isobutylene]] from ''tert''-butyl alcohol. A special kind of dehydration reaction involves [[triphenylmethanol]] and especially its amine-substituted derivatives. When treated with acid, these alcohols lose water to give stable carbocations, which are commercial dyes.<ref name="Gessner-2000">{{Ullmann's | last1 = Gessner | first1 = Thomas | last2 = Mayer | first2 = Udo | title = Triarylmethane and Diarylmethane Dyes | year = 2000 | doi = 10.1002/14356007.a27_179}}</ref>
[[image:Kristallviolett Darstellung.svg|class=skin-invert-image|thumb|right|322px|Preparation of [[crystal violet]] by protonolysis of the tertiary alcohol.]]

===Esterification===
Alcohol and [[carboxylic acid]]s react in the so-called [[Fischer esterification]]. The reaction usually requires a [[catalyst]], such as concentrated sulfuric acid:
:{{chem2 | R\sOH + R'\sCO2H -> R'\sCO2R + H2O }}
Other types of ester are prepared in a similar manner−for example, [[tosyl]] (tosylate) esters are made by reaction of the alcohol with [[4-toluenesulfonyl chloride]] in [[pyridine]].

===Oxidation===
{{Main|Alcohol oxidation}}
Primary alcohols ({{chem2|R\sCH2OH}}) can be oxidized either to [[aldehyde]]s ({{chem2|R\sCHO}}) or to [[carboxylic acid]]s ({{chem2|R\sCO2H}}). The oxidation of secondary alcohols ({{chem2|R^{1}R^{2}CH\sOH}}) normally terminates at the [[ketone]] ({{chem2|R^{1}R^{2}C\dO}}) stage. Tertiary alcohols ({{chem2|R^{1}R^{2}R^{3}C\sOH}}) are resistant to oxidation.

The direct oxidation of primary alcohols to carboxylic acids normally proceeds via the corresponding aldehyde, which is transformed via an ''aldehyde hydrate'' ({{chem2|R\sCH(OH)2}}) by reaction with water before it can be further oxidized to the carboxylic acid.

[[File:Alcohol to aldehyde to acid.png|class=skin-invert-image|upright=2.25|thumb|center|Mechanism of oxidation of primary alcohols to carboxylic acids via aldehydes and aldehyde hydrates]]

Reagents useful for the transformation of primary alcohols to aldehydes are normally also suitable for the oxidation of secondary alcohols to ketones. These include [[Collins reagent]] and [[Dess–Martin periodinane]]. The direct oxidation of primary alcohols to carboxylic acids can be carried out using [[potassium permanganate]] or the [[Jones reagent]].

==See also==
{{div col|colwidth=20em}}
* [[Beer chemistry]]
* [[Enol]]
* [[Ethanol fuel]]
* [[Fatty alcohol]]
* [[Index of alcohol-related articles]]
* [[List of alcohols]]
* [[Lucas' reagent|Lucas test]]
* [[Polyol]]
* [[Rubbing alcohol]]
* [[Sugar alcohol]]
* [[Transesterification]]
* [[Wine chemistry]]
{{div col end}}

== Notes ==
{{Notelist}}

== Citations ==
{{Reflist|30em}}

== General references ==
* {{cite book |last=Metcalf |first=Allan A. |year=1999 |title=The World in So Many Words |publisher=Houghton Mifflin |isbn=0-395-95920-9 <!--|url=https://books.google.com/books?id=4O0W5XyQVCYC&pg=PA123#PPA123,M1-->}}

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