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<h3>Learning Objective</h3>
<ul>
<li>Recognize the chemical principles of condensation <a data-lesson="reactions-2" data-subject="chemistry" data-tutorial="metals-metalloids-nonmetals" href="https://app.ulearngo.com/chemistry/metals-metalloids-nonmetals/reactions-2">reactions</a> as they relate to polymerization.</li>
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<h3>Key Points</h3>
<ul>
<li>During condensation reaction, two molecules combine to form a single molecule with the loss of a small molecule; in dehydration reaction, this lost molecule is water.</li>
<li>Intermolecular condensation occurs between two separate molecules, while intramolecular condensation is the union between <a data-lesson="chemical-formulas" data-subject="chemistry" data-tutorial="atoms-molecules-ions" href="https://app.ulearngo.com/chemistry/atoms-molecules-ions/chemical-formulas">atoms</a> or groups of the same molecule, often leading to ring formation.</li>
<li>Condensation reactions are used in condensation polymerization, when a <a data-lesson="radioactive-decay-series" data-subject="chemistry" data-tutorial="nuclear-chemistry" href="https://app.ulearngo.com/chemistry/nuclear-chemistry/radioactive-decay-series">series</a> of condensation steps form long chains; this reaction may be either a homopolymerization of a single monomer or a copolymerization of two co-monomers; many biological transformations are condensation reactions.</li>
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<h3>Terms</h3>
<ul>
<li><strong>condensation polymerization:</strong> a polymerization mechanism in which <a data-lesson="types-of-biological-macromolecules" data-subject="chemistry" data-tutorial="organic-chemistry" href="https://app.ulearngo.com/chemistry/organic-chemistry/types-of-biological-macromolecules">monomers</a> react to form dimers first, then trimers, longer oligomers, and eventually long chain polymers</li>
<li><strong>condensation reaction:</strong> any reaction in which two molecules react with the resulting loss of a water molecule (or other small molecule); the formal reverse of hydrolysis</li>
<li><strong>dehydration reaction:</strong> an elimination (condensation) reaction in which the small molecule that is removed is water</li>
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<p>In a condensation reaction, two molecules or parts thereof combine, releasing a small molecule. When this small molecule is water, it is known as a dehydration reaction. Other possible lost molecules include <a data-lesson="hydrogen-reactions" data-subject="chemistry" data-tutorial="metals-metalloids-nonmetals" href="https://app.ulearngo.com/chemistry/metals-metalloids-nonmetals/hydrogen-reactions">hydrogen</a> chloride, methanol, and acetic acid.</p>
<p>When two separate molecules react, their condensation is termed intermolecular. A simple example is the condensation of two amino acids to form a peptide. This reaction example is the reverse of hydrolysis, which splits a chemical entity into two parts through action from the <a data-lesson="polar-molecules" data-subject="chemistry" data-tutorial="bonding-atomic-combinations" href="https://app.ulearngo.com/chemistry/bonding-atomic-combinations/polar-molecules">polar</a> water molecule, which itself splits into hydroxide and hydrogen ions.</p>
<div class="wp-caption alignnone" id="attachment_322367" style="width: 576px"><img alt="" class="size-full wp-image-322367" height="134" src="https://data.ulearngo.com/assets/79dcfb6d-243f-45d5-8f5f-83c47f561be8" width="576"/><p class="wp-caption-text"><b>Peptide bond formed during condensation reaction</b>: The condensation (dehydration) of two amino acids to form a peptide bond (red) with expulsion of water (blue).</p></div>
<p>When a condensation is performed between different parts of the same molecule, the reaction is termed intramolecular condensation; in many cases, this leads to ring formation. An example is the Dieckmann condensation, in which the two <a data-lesson="production-of-esters" data-subject="chemistry" data-tutorial="organic-molecules" href="https://app.ulearngo.com/chemistry/organic-molecules/production-of-esters">ester</a> groups of a single diester molecule react with each other to lose a small alcohol molecule and form a β-ketoester product.</p>
<p>Many condensation reactions follow a nucleophilic acyl <a data-lesson="addition-elimination-and-substitution-reactions" data-subject="chemistry" data-tutorial="organic-molecules" href="https://app.ulearngo.com/chemistry/organic-molecules/addition-elimination-and-substitution-reactions">substitution</a> or an aldol condensation reaction mechanism (see previous concept for more information). Other condensations, such as the acyloin condensation, are triggered by radical conditions.</p>
<h2>Condensation Polymerization Reactions</h2>
<p>In one type of polymerization reaction, a series of condensation steps takes place whereby monomers or monomer chains add to each other to form longer chains. This is termed “condensation polymerization,” or “step-growth polymerization,” and occurs in such processes as the synthesis of polyesters or nylons. Nylon is a silky material used to make clothes made of repeating <a data-lesson="ideal-gas-laws" data-subject="chemistry" data-tutorial="states-of-matter" href="https://app.ulearngo.com/chemistry/states-of-matter/ideal-gas-laws">units</a> linked by amide bonds, and is frequently referred to as polyamide. This reaction may be either a homopolymerization of a single monomer A-B with two different end groups that condense, or a copolymerization of two co-monomers A-A and B-B. Small molecules are usually liberated in these condensation steps, unlike polyaddition reactions.</p>
<div class="wp-caption alignnone" id="attachment_322366" style="width: 800px"><img alt="Condensation of diacid and diamine: The condensation of a diacid and diamine is an example of A-B polymerization." class="wp-image-322366 size-full" height="114" src="https://data.ulearngo.com/assets/18eaa182-44aa-4a9f-bc81-1045c389ce50" width="800"/><p class="wp-caption-text"><b>Condensation of diacid and diamine</b>: The condensation of a diacid and diamine is an example of A-B polymerization.</p></div>
<p>Condensation <a data-lesson="types-of-synthetic-organic-polymers" data-subject="chemistry" data-tutorial="organic-chemistry" href="https://app.ulearngo.com/chemistry/organic-chemistry/types-of-synthetic-organic-polymers">polymers</a> often require heat, form slower than do addition polymers, and are lower in molecular weight. This type of reaction is used as a basis for making many important polymers, such as nylon, polyester, and various epoxies. It is also the basis for the laboratory formation of silicates and polyphosphates. Many biological transformations, such as polypeptide synthesis, polyketide synthesis, terpene syntheses, phosphorylation, and glycosylations are condensations.</p>
<div class="wp-caption alignnone" style="width: 680px"><img alt="Nylon molecular structure: Nylon is a synthetic polymer produced by condensation polymerization." height="430" src="https://data.ulearngo.com/assets/55549696-7bb5-429f-8af0-a3d8d3a6d99b" width="680"/><p class="wp-caption-text"><b>Nylon molecular structure</b>: Nylon is a synthetic polymer produced by condensation polymerization.</p></div>

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Condensation Reactions

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Condensation Reactions

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