Transesterification

<h2 id="mechanism">Mechanism</h2>
<p>In the transesterification mechanism, the carbonyl carbon of the starting ester reacts to give a <a href="/facts/Tetrahedral_molecular_geometry/583AL1sP">tetrahedral</a> intermediate, which either reverts back to the starting material, or proceeds to the transesterified product (RCOOR2). The various species exist in equilibrium, and the product distribution depends on the relative energies of the reactant and product. Depending on reaction conditions <a href="/facts/Ester_hydrolysis/FoUAIIw4">ester hydrolysis</a> and/or <a href="/facts/Esterification/FoUAIIw4">esterification</a> will also occur, which results in some amount of free carboxylic acid being present.
</p>

<h2 id="applications">Applications</h2>
<h3>Polyester production</h3>
<p>The largest scale application of transesterification is in the synthesis of <a href="/facts/Polyester/Ivp9CHpl">polyesters</a>.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> In this application, diesters undergo transesterification with diols to form macromolecules. For example, <a href="/facts/Dimethyl_terephthalate/1rbHIv7A">dimethyl terephthalate</a> and <a href="/facts/Ethylene_glycol/stFz6CVe">ethylene glycol</a> react to form <a href="/facts/Polyethylene_terephthalate/Sc5UhmCB">polyethylene terephthalate</a> and <a href="/facts/Methanol/EIfpoNCg">methanol</a>, which is evaporated to drive the reaction forward.
</p>
<h3>Methanolysis and biodiesel production</h3>
<p>The reverse reaction, methanolysis, is also an example of transesterification. This process has been used to recycle polyesters into individual monomers (see <a href="/facts/Plastic_recycling/uk9fne5K">plastic recycling</a>). It is also used to convert fats (<a href="/facts/Triglyceride/BQmjv4A0">triglycerides</a>) into <a href="/facts/Biodiesel/M6FkfJXH">biodiesel</a>. This conversion was one of the first uses. Transesterified <a href="/facts/Vegetable_oil/70v8uQMH">vegetable oil</a> (<a href="/facts/Biodiesel/M6FkfJXH">biodiesel</a>) was used to power heavy-duty vehicles in South Africa before <a href="/facts/World_War_II/2efV5L1U">World War II</a>.
</p><p>It was <a href="/facts/Patented/LjT2bG3A">patented</a> in the US in the 1950s by <a href="/facts/Colgate-Palmolive/BlXKtc0v">Colgate</a>, though <a href="/facts/Biolipid/TdQR87HX">biolipid</a> transesterification may have been discovered much earlier. In the 1940s, researchers were looking for a method to more readily produce <a href="/facts/Glycerol/sRQ6NBQQ">glycerol</a>, which was used to produce <a href="/facts/Explosives/sUme5Pp8">explosives</a> for World War II. Many of the methods used today by producers have their origin in the original 1940s research.
</p><p>Biolipid transesterification has also been recently shown by Japanese researchers to be possible using a <a href="/facts/Supercritical_fluid/rGkUWb7e">supercritical</a> methanol methodology, whereby high temperature, high-pressure vessels are used to physically catalyze the biolipid/methanol reaction into fatty-acid methyl esters.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a>
</p>
<h3>Fat processing</h3>
<p><a href="/facts/Fat_interesterification/L02ADdq2">Fat interesterification</a> is used in the <a href="/facts/Food_industry/1JPhss6V">food industry</a> to rearrange the <a href="/facts/Fatty_acid/JGg3erIu">fatty acids</a> of <a href="/facts/Triglyceride/BQmjv4A0">triglycerides</a> in edible <a href="/facts/Fat/87HcP11s">fats</a> and <a href="/facts/Vegetable_oil/70v8uQMH">vegetable oils</a>. For example, a solid fat with mostly saturated fatty acids may be transesterified with a vegetable oil having high unsaturated acid contents, to produce a spreadable semisolid fat whose molecules have a mix both kinds of acids.
</p>
<h3>Synthesis</h3>
<p>Transesterification is used to synthesize <a href="/facts/Enol/aySJNbQx">enol</a> derivatives, which are difficult to prepare by other means. <a href="/facts/Vinyl_acetate/qVdoopEo">Vinyl acetate</a>, which is cheaply available, undergoes transesterification, giving access to <a href="/facts/Enol_ether/rYjf1BBD">vinyl ethers</a>:<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a><a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a>
</p>
ROH + AcOCH=CH2 ⟶ ROCH=CH2 + AcOH
<p>The reaction can be effected with high enantioselectivity when mediated with a <a href="/facts/Lipase/nPgIyNBS">lipase</a>.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a>
</p>
<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Biodiesel_production/1y0cmUWn">Biodiesel production</a></li>
<li><a href="/facts/Otera%2527s_catalyst/7SGAvzRq">Otera's catalyst</a></li>
<li><a href="/facts/Transalkylation/UmAdc2UB">Transalkylation</a></li>
<li><a href="/facts/Transamidification/quMB0G1b">Transamidification</a></li>
<li><a href="/facts/Cocaethylene/5CLpxhxl">Cocaethylene</a></li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>Otera, Junzo. (June 1993). "Transesterification". Chemical Reviews. 93 (4): 1449–1470. doi:10.1021/cr00020a004. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>"ENZYME – 3.1.1.3 Triacylglycerol lipase". enzyme.expasy.org. SIB Swiss Institute of Bioinformatics. Retrieved 17 February 2021. <a href="https://enzyme.expasy.org/EC/3.1.1.3" target="_blank">https://enzyme.expasy.org/EC/3.1.1.3</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>Wilhelm Riemenschneider1 and Hermann M. Bolt "Esters, Organic" Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. doi:10.1002/14356007.a09_565.pub2 <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>Ehimen, E. A.; Sun, Z. F.; Carrington, C. G. (1 March 2010). "Variables affecting the in situ transesterification of microalgae lipids". Fuel. 89 (3): 677–684. doi:10.1016/j.fuel.2009.10.011. ISSN 0016-2361. <a href="https://www.sciencedirect.com/science/article/pii/S0016236109004736" target="_blank">https://www.sciencedirect.com/science/article/pii/S0016236109004736</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
<li id="fn:5"><p>Tomotaka Hirabayashi; Satoshi Sakaguchi; Yasutaka Ishii (2005). "Iridium-catalyzed Synthesis of Vinyl Ethers from Alcohols and Vinyl Acetate". Org. Synth. 82: 55. doi:10.15227/orgsyn.082.0055. <a href="https://doi.org/10.15227%2Forgsyn.082.0055" target="_blank">https://doi.org/10.15227%2Forgsyn.082.0055</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li>
<li id="fn:6"><p>Yasushi Obora; Yasutaka Ishii (2012). "Discussion Addendum: Iridium-catalyzed Synthesis of Vinyl Ethers from Alcohols and Vinyl Acetate". Org. Synth. 89: 307. doi:10.15227/orgsyn.089.0307. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li>
<li id="fn:7"><p>Manchand, Percy S. (2001). "Vinyl Acetate". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rv008. ISBN 0-471-93623-5. <a href="0-471-93623-5" target="_blank">0-471-93623-5</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li>
</ol>

Transesterification open-in-new

Transesterification