Homologation reaction

In <a href="/facts/Organic_chemistry/djxhxaNg">organic chemistry</a>, a homologation reaction, also known as homologization, is any <a href="/facts/Chemical_reaction/GpqWlKrz">chemical reaction</a> that converts the <a href="/facts/Reactant/c3GLInCu">reactant</a> into the next member of the <a href="/facts/Homologous_series/7PKCuvzm">homologous series</a>. A homologous series is a group of compounds that differ by a constant unit, generally a <a href="/facts/Methylene_bridge/t3lvUJuT">methylene</a> (−CH2−) group. The reactants undergo a homologation when the number of a repeated <a href="/facts/Structural_unit/XGlAYDb0">structural unit</a> in the molecules is increased. The most common homologation reactions increase the number of methylene (−CH2−) units in <a href="/facts/Saturated_and_unsaturated_compounds/tde2C216">saturated chain</a> within the molecule. For example, the reaction of <a href="/facts/Aldehyde/xSIRkW03">aldehydes</a> or <a href="/facts/Ketone/BqQXpLo4">ketones</a> with <a href="/facts/Diazomethane/KyBPQTGb">diazomethane</a> or <a href="/facts/Methoxymethylenetriphenylphosphine/KmmXzAxf">methoxymethylenetriphenylphosphine</a> to give the next homologue in the series.
Examples of homologation reactions include:

<ul><li><a href="/facts/Kiliani-Fischer_synthesis/MIydSWPa">Kiliani-Fischer synthesis</a>, where an <a href="/facts/Aldose/hKGwqzFj">aldose</a> molecule is elongated through a three-step process consisting of:
<ol><li><a href="/facts/Nucleophillic_addition/1HL9WlD6">Nucleophillic addition</a> of cyanide to the carbonyl to form a <a href="/facts/Cyanohydrin/enG37w2u">cyanohydrin</a></li>
<li>Hydrolysis to form a <a href="/facts/Lactone/UMgRUFtj">lactone</a></li>
<li>Reduction to form the homologous aldose</li></ol></li>
<li><a href="/facts/Wittig_reaction/7Cjao2HI">Wittig reaction</a> of an aldehyde with <a href="/facts/Methoxymethylenetriphenylphosphine/KmmXzAxf">methoxymethylenetriphenylphosphine</a>, which produces a homologous aldehyde.</li>
<li><a href="/facts/Arndt%25E2%2580%2593Eistert_reaction/bEYwno2L">Arndt–Eistert reaction</a> is a series of chemical reactions designed to convert a carboxylic acid to a higher carboxylic acid homologue (i.e. contains one additional carbon atom)</li>
<li><a href="/facts/Kowalski_ester_homologation/vfqSNVP7">Kowalski ester homologation</a>, an alternative to the Arndt-Eistert synthesis. Has been used to convert β-amino esters from α-amino esters through an <a href="/facts/Ynolate/lPXEMufI">ynolate</a> intermediate.</li>
<li><a href="/facts/Seyferth%25E2%2580%2593Gilbert_homologation/Xyr5N7m2">Seyferth–Gilbert homologation</a> in which an aldehyde is converted to a terminal alkyne and then hydrolyzed back to an aldehyde.</li></ul>
Some reactions increase the chain length by more than one unit. For example, the <a href="/facts/DeMayo_reaction/vVKK9rvT">DeMayo reaction</a> can be considered a two-carbon homologation reaction.

Homologation reaction open-in-new

Homologation reaction