Misplaced Pages

This is an old revision of this page, as edited by 73.210.155.96 (talk) at 18:02, 29 March 2017 (Restructured to begin transform from a cut and paste sixth form draft essay into an article. Note, no time today for forensic sourcing of the original offending text. Only came to read to see if the content was good enough to assign.). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

This article does not cite any sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Condensation reaction" – news · newspapers · books · scholar · JSTOR (Learn how and when to remove this message)

A condensation reaction is a chemical reaction in which two molecules or moieties, often functional groups, combine to form a larger molecule, together with the loss of a small molecule. Possible small molecules that are lost include water, acetic acid, hydrogen chloride, or methanol, but most commonly in biological reactions it is water. Condensations producing water as a byproduct are the opposite reaction of transformations involving hydrolysis, which split a reactant into two new species through addition of a water molecule.

Condensation can be intermolecular (between two different molecules) or intramolecular (involving different groups within the same molecule). A simple example of an intermolecular condensation is the joining of two amino acids in the peptide bond, as is characteristic of all proteins. Examples of intermolecular condensations often lead to ring formation, and include the synthesis of cyclic peptides via the same bond forming process as just described, as well as Dieckmann condensations, in which the two ester groups within a diester molecule react with release of an alcohol molecule to form a β-ketoester product.

Mechanisms

This section needs expansion with: an encyclopedic description of the mechanisms by condensation reactions occur (e.g., as in Carey & Sundberg or March). You can help by adding to it.

Condensation reactions can follow a variety of different reaction mechanisms, depending on the groups reacting and the conditions employed to perform the reaction (solvent, temperature, reaction additives, etc.).

Applications

This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (Learn how and when to remove this message)

This section may contain unverified or indiscriminate information in embedded lists. Please help clean up the lists by removing items or incorporating them into the text of the article.

Many artificial, man-made chemical reactions, and many biological transformations are condensation reactions. In the latter case (reactions in nature), phosphorylation and glycosylation reactions are generally all condensations, as are the key bond-forming reactions in all polypeptide and polynucleotide syntheses, and much of polyketide and terpene biosynthesis as well. Examples of the large number of condensation reactions are used in synthetic organic chemistry include:

• Acyloin condensation
• Aldol condensation
• Claisen condensation
• Claisen–Schmidt condensation
• Darzens reaction (glycidic ester condensation)
• Dieckmann condensation
• Guareschi–Thorpe condensation
• Knoevenagel condensation
• Pechmann condensation
• Rap–Stoermer condensation
• Self-condensation or symmetrical aldol condensation
• Thorpe–Ziegler reaction

The reactions that form acid anhydrides from their constituent acids are also typically condensation reactions.

Condensation polymerization

This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (Learn how and when to remove this message)

This article may require cleanup to meet Misplaced Pages's quality standards. The specific problem is: the current array of sentences fails as encyclopedic, lacking the scope, structure, details, examples, and sources of even a stub section compliant with WP:VERIFY. Please help improve this article if you can. (Learn how and when to remove this message)

Condensation polymerization produces many important polymers, for example: nylon, polyester, and other condensation polymers and various epoxies. It is also the basis for the laboratory formation of silicates and polyphosphates. In condensation polymerization or "step-growth polymerization", multiple condensation reactions take place, joining monomers and monomer chains into long chains called polymers. It occurs for example in the synthesis of polyesters or nylons. It can be homopolymerization of a single monomer A-B with two different end groups that condense, or copolymerization of two co-monomers A-A and B-B.

Condensation polymerization releases multiple small molecules, in contrast to polyaddition reactions, which do not. 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, per Carothers' equation.

Bifunctional monomers lead to linear chains, and therefore thermoplastic polymers, but, when the monomer functionality exceeds two, the product is a branched chain that may be a thermosetting polymer.

See also

• Anabolism
• Hydrolysis, the opposite of a condensation reaction
• Condensed tannins

References

1. IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (1994) "Condensation Reaction". doi:10.1351/goldbook.C01238

• Condensation reactions