Editing Condensation reaction (section)

{{short description|Chemical reaction in which two molecules are combined and a small molecule, usually water, is lost}}

In [[organic chemistry]], a '''condensation reaction''' is a type of [[chemical reaction]] in which two [[molecule]]s are [[Combination reaction|combined]] to form a single molecule, usually with the loss of a small molecule such as [[water]].<ref>{{cite book |title=Book: Introductory Chemistry (CK-12) |date=12 August 2020 |publisher=Chemistry Libre Texts |url=https://chem.libretexts.org/Bookshelves/Introductory_Chemistry/Book%3A_Introductory_Chemistry_(CK-12)/25%3A_Organic_Chemistry/25.18%3A_Condensation_Reactions |access-date=9 January 2021 |chapter=25.18 Condensation Reactions}}</ref> If water is lost, the reaction is also known as a [[dehydration reaction|dehydration synthesis]]. However other molecules can also be lost, such as [[ammonia]], [[ethanol]], [[acetic acid]] and [[hydrogen sulfide]].<ref>{{cite journal|url=https://goldbook.iupac.org/html/C/C01238.html|title=Condensation Reaction|website=IUPAC Compendium of Chemical Terminology (Gold Book)|year=2014|publisher=IUPAC|doi=10.1351/goldbook.C01238|access-date=7 December 2017|doi-access=free}}</ref>

The addition of the two molecules typically proceeds in a step-wise fashion to the addition product, usually in [[Chemical equilibrium|equilibrium]], and with loss of a water molecule (hence the name [[condensation]]).<ref>{{Cite journal|last=Fakirov|first=S.|date=2019-02-01|title=Condensation Polymers: Their Chemical Peculiarities Offer Great Opportunities|journal=Progress in Polymer Science|volume=89|pages=1–18|doi=10.1016/j.progpolymsci.2018.09.003|s2cid=105101288|issn=0079-6700}}</ref> The reaction may otherwise involve the [[functional group]]s of the molecule, and is a versatile class of reactions that can occur in [[acid]]ic or [[Base (chemistry)|basic]] conditions or in the presence of a [[catalyst]]. This class of reactions is a vital part of life as it is essential to the formation of [[peptide bond]]s between [[amino acid]]s and to the [[biosynthesis of fatty acids]].<ref>{{Cite book|title=Fundamentals of Biochemistry|url=https://archive.org/details/fundamentalsbioc00voet|url-access=limited|last1=Voet|first1=Donald|last2=Voet|first2=Judith|last3=Pratt|first3=Chriss|publisher=John Wiley & Sons, Inc.|year=2008|isbn=978-0470-12930-2|location=Hoboken, NJ|pages=[https://archive.org/details/fundamentalsbioc00voet/page/n118 88]}}</ref>

[[Image:AminoacidCondensation.svg|thumb|520 px| center|Idealized scheme showing condensation of two amino acids to give a [[peptide bond]].]]

Many variations of condensation reactions exist. Common examples include the [[aldol condensation]] and the [[Knoevenagel condensation]], which both form water as a by-product, as well as the [[Claisen condensation]] and the [[Dieckman condensation]] (intramolecular Claisen condensation), which form alcohols as by-products.<ref name=":0">{{cite book|title=Advanced Organic Chemistry|url=https://archive.org/details/advancedorganicc00bruc|url-access=limited|last1=Bruckner|first1=Reinhard|date=2002|publisher=Harcourt Academic Press|isbn=0-12-138110-2|edition=First|location=San Diego, California|pages=[https://archive.org/details/advancedorganicc00bruc/page/n419 414]–427}}</ref>

[[File:Condensationaldolique.png|alt=Aldol condensation overview|588x588px]]