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==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}}</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]].
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