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{{short description|Chemical reaction in which two molecules are combined and a small molecule, usually water, is lost}}
⚫ ]s to form a ] (red) with expulsion of water (blue)]]
A '''condensation reaction''', also commonly referred to as dehydration synthesis, is a ] in which two ]s or moieties (]) combine to form a larger molecule, together with the loss of a small molecule.<ref name="Gold">{{GoldBookRef|title=Condensation Reaction|file=C01238|year=1994}}</ref> Possible small molecules lost are ], ], ], or ] but most commonly in a biological reaction it is ]. The word "condensation" suggests a process in which two or more things are brought "together" (Latin "con") to form something "dense", like in condensation from gaseous to liquid state of matter; this does not imply, however, that condensation reaction products have greater density than reactants.


In ], a '''condensation reaction''' is a type of ] in which two ]s are ] to form a single molecule, usually with the loss of a small molecule such as ].<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 ]. However other molecules can also be lost, such as ], ], ] and ].<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>
When two separate molecules react, the condensation is termed ]. A simple example is the condensation of two ]s to form the ] characteristic of ]. This reaction example is the opposite of ], which splits a chemical entity into two parts through the action of the polar water molecule, which itself splits into ] and ] ions. Hence energy is required.


The addition of the two molecules typically proceeds in a step-wise fashion to the addition product, usually in ], and with loss of a water molecule (hence the name ]).<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 ]s of the molecule, and is a versatile class of reactions that can occur in ]ic or ] conditions or in the presence of a ]. This class of reactions is a vital part of life as it is essential to the formation of ]s between ]s and to the ].<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=}}</ref>
If the union is between atoms or groups of the same molecule, the reaction is termed ] condensation, and in many cases leads to ring formation. An example is the ], in which the two ] groups of a single diester molecule react with each other to lose a small ] molecule and form a β-ketoester product.


⚫ ].]]
]


Many variations of condensation reactions exist. Common examples include the ] and the ], which both form water as a by-product, as well as the ] and the ] (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=–427}}</ref>
==Mechanism==
Many condensation reactions follow a ] or an ] ]. Other condensations, such as the ] are triggered by ] or ] conditions.


]
==Condensation reactions in polymer chemistry==
In one type of polymerization reaction, a series of condensation steps take place whereby ]s or monomer chains add to each other to form longer chains. This is termed 'condensation polymerization' or ']', and occurs for example in the synthesis of ]s or ]s. It may be either a homopolymerization of a single monomer A-B with two different end groups that condense or a ]ization of two co-monomers A-A and B-B. Small molecules are usually liberated in these condensation steps, in contrast to ] reactions with no liberation of small molecules.


== Synthesis of prebiotic molecules ==
In general, condensation polymers form more slowly than addition polymers, often requiring heat. They are generally lower in molecular weight. Monomers are consumed early in the reaction; the terminal functional groups remain active throughout and short chains combine to form longer chains. A high conversion rate is required to achieve high molecular weights as per ].
{{main|Abiogenesis}}

Condensation reactions likely played major roles in the synthesis of the first biotic molecules including early ]s and ]s. In fact, condensation reactions would be required at multiple steps in ] oligomerization: the condensation of ]s and ]s, ] ], and ] polymerization.<ref name=":02">{{Cite book |last=Fiore |first=Michele |title=Prebiotic Chemistry and Life's Origin |publisher=Royal Society of Chemistry |year=2022 |isbn=9781839164804 |location=United Kingdom |pages=124–144}}</ref>
Bifunctional monomers lead to linear chains (and therefore ] polymers), but, when the monomer ] exceeds two, the product is a ] chain that may yield a ] polymer.

==Applications==
This type of reaction is used as a basis for the making of many important ]s, for example: ], ], and other ]s and various ]. It is also the basis for the laboratory formation of ]s and ]s. The reactions that form acid ]s from their constituent acids are typically condensation reactions.

Many biological transformations are condensation reactions. ], ] synthesis, ] syntheses, ], and ]s are a few examples of this reaction.

A large number of such reactions are used in synthetic organic chemistry. Other examples include:

*]
*]
*] (this is not technically a condensation, but is called so for historical reasons)<ref name="Gold"/>
*]
*]
*] (glycidic ester condensation)
*]
*]
*]
*]
*]
*]
*] or symmetrical aldol condensation
*]

See ]


==See also== ==See also==
* ] * ]
* ] * ], the opposite of a condensation reaction
* ]s * ]s


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Latest revision as of 17:03, 23 December 2024

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 molecules are combined to form a single molecule, usually with the loss of a small molecule such as water. If water is lost, the reaction is also known as a dehydration synthesis. However other molecules can also be lost, such as ammonia, ethanol, acetic acid and hydrogen sulfide.

The addition of the two molecules typically proceeds in a step-wise fashion to the addition product, usually in equilibrium, and with loss of a water molecule (hence the name condensation). The reaction may otherwise involve the functional groups of the molecule, and is a versatile class of reactions that can occur in acidic or 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 bonds between amino acids and to the biosynthesis of fatty acids.

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.

Aldol condensation overview

Synthesis of prebiotic molecules

Main article: Abiogenesis

Condensation reactions likely played major roles in the synthesis of the first biotic molecules including early peptides and nucleic acids. In fact, condensation reactions would be required at multiple steps in RNA oligomerization: the condensation of nucleobases and sugars, nucleoside phosphorylation, and nucleotide polymerization.

See also

References

  1. "25.18 Condensation Reactions". Book: Introductory Chemistry (CK-12). Chemistry Libre Texts. 12 August 2020. Retrieved 9 January 2021.
  2. "Condensation Reaction". IUPAC Compendium of Chemical Terminology (Gold Book). IUPAC. 2014. doi:10.1351/goldbook.C01238. Retrieved 7 December 2017.
  3. Fakirov, S. (2019-02-01). "Condensation Polymers: Their Chemical Peculiarities Offer Great Opportunities". Progress in Polymer Science. 89: 1–18. doi:10.1016/j.progpolymsci.2018.09.003. ISSN 0079-6700. S2CID 105101288.
  4. Voet, Donald; Voet, Judith; Pratt, Chriss (2008). Fundamentals of Biochemistry. Hoboken, NJ: John Wiley & Sons, Inc. pp. 88. ISBN 978-0470-12930-2.
  5. Bruckner, Reinhard (2002). Advanced Organic Chemistry (First ed.). San Diego, California: Harcourt Academic Press. pp. 414–427. ISBN 0-12-138110-2.
  6. Fiore, Michele (2022). Prebiotic Chemistry and Life's Origin. United Kingdom: Royal Society of Chemistry. pp. 124–144. ISBN 9781839164804.
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