This article is about chemical reactions resulting in the loss of water from a molecule. For the removal of water from solvents and reagents, see Desiccation.
The classic example of a dehydration reaction is the Fischer esterification, which involves treating a carboxylic acid with an alcohol to give an ester
RCO2H + R′OH ⇌ RCO2R′ + H2O
Often such reactions require the presence of a dehydrating agent, i.e. a substance that reacts with water.
Alkenes can be made from alcohols by dehydration. This conversion, among others, is used in converting biomass to liquid fuels.[2] The conversion of ethanol to ethylene is a fundamental example:[3][4]
CH3CH2OH → H2C=CH2 + H2O
The reaction is accelerated by acid catalysts such as sulfuric acid and certain zeolites. These reactions often proceed via carbocation]]ic intermediates as shown for the dehydration of cyclohexanol.[5]
Some alcohols are prone to dehydration. 3-Hydroxylcarbonyls, called aldols, release water upon standing at room temperature:
RC(O)CH2CH(OH)R' → RC(O)CH=CHR' + H2O
The reaction is induced by dehydrating reagents. For example, 2-methyl-cyclohexan-1-ol dehydrates to 1-methylcyclohexene in the presence of Martin's sulfurane, which reacts irreversibly with water.[6][7]
^Besson, Michèle; Gallezot, Pierre; Pinel, Catherine (2014-02-12). "Conversion of Biomass into Chemicals over Metal Catalysts". Chemical Reviews. 114 (3): 1827–1870. doi:10.1021/cr4002269. ISSN 0009-2665. PMID 24083630.
^Zimmermann, Heinz; Walz, Roland (2008). "Ethylene". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a10_045.pub3. ISBN978-3527306732.
^G. H. Coleman, H. F. Johnstone (1925). "Cyclohexene". Organic Syntheses. 5: 33. doi:10.15227/orgsyn.005.0033.
^J. Brent Friesen; Robert Schretzman (2011). "Dehydration of 2-Methyl-1-cyclohexanol: New Findings from a Popular Undergraduate Laboratory Experiment". J. Chem. Educ.88 (8): 1141–1147. Bibcode:2011JChEd..88.1141F. doi:10.1021/ed900049b.
^Roden, Brian A. (2001). "Diphenylbis(1,1,1,3,3,3-hexafluoro-2-phenyl-2-propoxy)sulfurane". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rd409. ISBN0471936235.
^Katryniok, Benjamin; Paul, Sébastien; Bellière-Baca, Virginie; Rey, Patrick; Dumeignil, Franck (2010). "Glycerol dehydration to acrolein in the context of new uses of glycerol". Green Chemistry. 12 (12): 2079. doi:10.1039/c0gc00307g. ISSN 1463-9262.
^Franz Wirsching "Calcium Sulfate" in Ullmann's Encyclopedia of Industrial Chemistry, 2012 Wiley-VCH, Weinheim. doi:10.1002/14356007.a04_555
^Staff. . LaFargePrestia. Archived from the original on November 20, 2008. Retrieved 27 November 2008.
February 15, 2024
dehydration, reaction, this, article, about, chemical, reactions, resulting, loss, water, from, molecule, removal, water, from, solvents, reagents, desiccation, chemistry, dehydration, reaction, chemical, reaction, that, involves, loss, water, from, reacting, . This article is about chemical reactions resulting in the loss of water from a molecule For the removal of water from solvents and reagents see Desiccation In chemistry a dehydration reaction is a chemical reaction that involves the loss of water from the reacting molecule or ion Dehydration reactions are common processes the reverse of a hydration reaction Contents 1 Dehydration reactions in organic chemistry 1 1 Esterification 1 2 Etherification 1 3 Nitrile formation 1 4 Ketene formation 1 5 Alkene formation 2 Dehydration reactions in inorganic chemistry 3 See also 4 ReferencesDehydration reactions in organic chemistry editEsterification edit The classic example of a dehydration reaction is the Fischer esterification which involves treating a carboxylic acid with an alcohol to give an ester RCO2H R OH RCO2R H2OOften such reactions require the presence of a dehydrating agent i e a substance that reacts with water Etherification edit Two monosaccharides such as glucose and fructose can be joined together to form saccharose using dehydration synthesis The new molecule consisting of two monosaccharides is called a disaccharide Nitrile formation edit Nitriles are often prepared by dehydration of primary amides RC O NH2 RCN H2OKetene formation edit Ketene is produced by heating acetic acid and trapping the product 1 CH3CO2H CH2 C O H2OAlkene formation edit Alkenes can be made from alcohols by dehydration This conversion among others is used in converting biomass to liquid fuels 2 The conversion of ethanol to ethylene is a fundamental example 3 4 CH3CH2OH H2C CH2 H2OThe reaction is accelerated by acid catalysts such as sulfuric acid and certain zeolites These reactions often proceed via carbocation ic intermediates as shown for the dehydration of cyclohexanol 5 nbsp nbsp Some alcohols are prone to dehydration 3 Hydroxylcarbonyls called aldols release water upon standing at room temperature RC O CH2CH OH R RC O CH CHR H2OThe reaction is induced by dehydrating reagents For example 2 methyl cyclohexan 1 ol dehydrates to 1 methylcyclohexene in the presence of Martin s sulfurane which reacts irreversibly with water 6 7 Double dehydration is illustrated by the conversion of glycerol to acrolein 8 9 nbsp Dehydration reactions in inorganic chemistry editThe formation of the pyrophosphate bond is an important dehydration relevant to bioenergetics Various construction materials are produced by dehydration Plaster of Paris is produced by dehydration of gypsum in a kiln 10 11 CaSO 4 2 H 2 O displaystyle ce CaSO4 2H2O nbsp heat displaystyle ce gt nbsp CaSO 4 1 2 H 2 O 1 1 2 H 2 O displaystyle ce CaSO4 1 2H2O 1 1 2H2O nbsp released as steam The resulting dry powder is ready to be mixed with water to form a stiff but workable paste that hardens See also editHydration reaction Condensation reaction HydrolysisReferences edit Miller Raimund Abaecherli Claudio Said Adel Jackson Barry 2001 Ketenes Ullmann s Encyclopedia of Industrial Chemistry Weinheim Wiley VCH doi 10 1002 14356007 a15 063 ISBN 978 3527306732 Besson Michele Gallezot Pierre Pinel Catherine 2014 02 12 Conversion of Biomass into Chemicals over Metal Catalysts Chemical Reviews 114 3 1827 1870 doi 10 1021 cr4002269 ISSN 0009 2665 PMID 24083630 Zimmermann Heinz Walz Roland 2008 Ethylene Ullmann s Encyclopedia of Industrial Chemistry Weinheim Wiley VCH doi 10 1002 14356007 a10 045 pub3 ISBN 978 3527306732 Zhang Minhua Yu Yingzhe 2013 07 17 Dehydration of Ethanol to Ethylene Industrial amp Engineering Chemistry Research 52 28 9505 9514 doi 10 1021 ie401157c ISSN 0888 5885 G H Coleman H F Johnstone 1925 Cyclohexene Organic Syntheses 5 33 doi 10 15227 orgsyn 005 0033 J Brent Friesen Robert Schretzman 2011 Dehydration of 2 Methyl 1 cyclohexanol New Findings from a Popular Undergraduate Laboratory Experiment J Chem Educ 88 8 1141 1147 Bibcode 2011JChEd 88 1141F doi 10 1021 ed900049b Roden Brian A 2001 Diphenylbis 1 1 1 3 3 3 hexafluoro 2 phenyl 2 propoxy sulfurane Encyclopedia of Reagents for Organic Synthesis doi 10 1002 047084289X rd409 ISBN 0471936235 H Adkins W H Hartung 1926 Acrolein Organic Syntheses 6 1 doi 10 15227 orgsyn 006 0001 Katryniok Benjamin Paul Sebastien Belliere Baca Virginie Rey Patrick Dumeignil Franck 2010 Glycerol dehydration to acrolein in the context of new uses of glycerol Green Chemistry 12 12 2079 doi 10 1039 c0gc00307g ISSN 1463 9262 Franz Wirsching Calcium Sulfate in Ullmann s Encyclopedia of Industrial Chemistry 2012 Wiley VCH Weinheim doi 10 1002 14356007 a04 555 Staff CaSO4 H2O LaFargePrestia Archived from the original on November 20 2008 Retrieved 27 November 2008 Retrieved from https en wikipedia org w index php title Dehydration reaction amp oldid 1195365982, wikipedia, wiki, book, books, library,
