Dehydration reaction - wikipedia Dehydration reaction 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 and the biological sciences, a dehydration reaction, also known as Zimmer 's Hydrogenesis, is a chemical reaction that involves the loss of a water molecule from the reacting molecule. Dehydration reactions are a subset of condensation reactions. Because the hydroxyl group ( -- OH ) is a poor leaving group, having a Brønsted acid catalyst often helps by protonating the hydroxyl group to give the better leaving group, -- OH. The reverse of a dehydration reaction is a hydration reaction. Common dehydrating agents used in organic synthesis include concentrated sulfuric acid, concentrated phosphoric acid, hot aluminium oxide and hot ceramic. Dehydration reactions and dehydration synthesis have the same meaning, and are often used interchangeably. Two monosaccharides, such as glucose and fructose, can be joined together ( to form sucrose ) using dehydration synthesis. The new molecule, consisting of two monosaccharides, is called a disaccharide. The process of hydrolysis is the reverse reaction, meaning that the water is recombined with the two hydroxyl groups and the disaccharide reverts to being monosaccharides. In the related condensation reaction water is released from two different reactants. Dehydration reactions In organic synthesis, there are many examples of dehydration reaction, for example dehydration of alcohols or sugars. Dehydration reactions Reaction Equation Conversion of alcohols to ethers 2 R -- OH → R -- O -- R + H O Conversion of alcohols to alkenes R -- CH CHOH -- R → R -- CH = CH -- R + H O for example the conversion of glycerol to acrolein : or the dehydration of 2 - methyl - 1 - cyclohexanol to ( mainly ) 1 - methylcyclohexene Conversion of carboxylic acids to acid anhydrides 2 RCOOH → ( RCO ) O + H O Conversion of amides to nitriles RCONH → R -- CN + H O Dienol benzene rearrangement Some dehydration reactions can be mechanistically complex, for instance the reaction of a sugar ( sucrose ) with concentrated sulfuric acid : to form carbon as a graphitic foam involves formation of carbon - carbon bonds. The reaction is driven by the strongly exothermic reaction as sulfuric acid reacts with water, which produces dangerous sulfuric - acid containing steam, therefore the experiment should only be performed in a fume - hood or well ventilated area. See also Hydration reaction References Jump up ^ H. Adkins ; W.H. Hartung ( 1926 ). `` Acrolein ''. Org. Synth. 6 : 1. doi : 10.15227 / orgsyn. 006.0001. ; Coll. Vol., 1, p. 15 Jump up ^ 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... 88.1141 F. doi : 10.1021 / ed900049b. Jump up ^ H. Plieninger ; Gunda Keilich ( 1956 ). `` Die Dienol - Benzol - Umlagerung '' ( The dienol - benzene rearrangement ). Angew. Chem. ( in German ). 68 ( 19 ) : 618. doi : 10.1002 / ange. 19560681914. Jump up ^ Margaret Jevnik Gentles ; Jane B. Moss ; Hershel L. Herzog ; E.B. Hershberg ( 1958 ). `` The Dienol - Benzene Rearrangement. Some Chemistry of 1, 4 - Androstadiene - 3, 17 - dione ''. J. Am. Chem. Soc. 80 ( 14 ) : 3702 -- 3705. doi : 10.1021 / ja01547a058. Jump up ^ youtube clip reaction sugar with sulfuric acid Jump up ^ http://www.exo.net/~pauld/activities/astronomy/transitvenus/sugarsulfuricacid.htm GND : 4226769 - 9 Retrieved from `` https://en.wikipedia.org/w/index.php?title=Dehydration_reaction&oldid=802386593 '' Categories : Elimination reactions Hidden categories : CS1 German - language sources ( de ) Wikipedia articles with GND identifiers Talk About Wikipedia Català Deutsch Eesti Español Français 한국어 Հայերեն Bahasa Indonesia Italiano Nederlands 日本 語 Norsk Português Русский Türkçe Українська 中文 Edit links This page was last edited on 25 September 2017, at 21 : 09. Text is available under the Creative Commons Attribution - ShareAlike License ; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia ® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization. About Wikipedia

Question: the results of dehydration reactions can be reversed by
Answer: hydration reaction