Fischer–Speier esterification

Fischer esterification or Fischer–Speier esterification is a special type of <a href="/facts/Esterification/FoUAIIw4">esterification</a> by <a href="/facts/Reflux/Elav2kgM">refluxing</a> a <a href="/facts/Carboxylic_acid/U4xuMosy">carboxylic acid</a> and an <a href="/facts/Alcohol_(chemistry)/Y0SCTDkh">alcohol</a> in the presence of an <a href="/facts/Acid_catalyst/JkJ7LkT6">acid catalyst</a>. The reaction was first described by <a href="/facts/Emil_Fischer/5wxbfBtu">Emil Fischer</a> and Arthur Speier in 1895. Most carboxylic acids are suitable for the reaction, but the alcohol should generally be primary or secondary. Tertiary alcohols are prone to <a href="/facts/Elimination_reaction/7LSBwU3P">elimination</a>. Contrary to common misconception found in organic chemistry textbooks, phenols can also be esterified to give good to near quantitative yield of products. Commonly used catalysts for a Fischer esterification include <a href="/facts/Sulfuric_acid/Wom6fymJ">sulfuric acid</a>, <a href="/facts/P-toluenesulfonic_acid/SFVDfI6a">p-toluenesulfonic acid</a>, and <a href="/facts/Lewis_acid/qlLqRvg2">Lewis acids</a> such as <a href="/facts/Scandium(III)_triflate/UEM9QYDE">scandium(III) triflate</a>. For more valuable or sensitive substrates (for example, <a href="/facts/Biomaterials/uBdFNr8I">biomaterials</a>) other, milder procedures such as <a href="/facts/Steglich_esterification/LSlYH4Rs">Steglich esterification</a> are used. The reaction is often carried out without a solvent (particularly when a large reagent excess of the alcohol reagent is used) or in a <a href="/facts/Solvent/LoMPMz8S">non-polar solvent</a> (e.g. <a href="/facts/Toluene/Pzdt8dwD">toluene</a>, <a href="/facts/Hexane/JxPecNPt">hexane</a>) that can facilitate <a href="/facts/Dean%25E2%2580%2593Stark_distillation/cARLn6f4">Dean–Stark distillation</a> to remove the water byproduct. Typical reaction times vary from 1–10 hours at temperatures of 60–110 °C.
Direct <a href="/facts/Acylation/9R8o69jN">acylations</a> of alcohols with carboxylic acids is preferred over acylations with <a href="/facts/Anhydride/9YnWCsJo">anhydrides</a> (poor <a href="/facts/Atom_economy/M8mPjCJw">atom economy</a> of the reaction) or <a href="/facts/Acid_chloride/R4ppUXre">acid chlorides</a> (moisture sensitive reagents). The main disadvantage of direct acylation is the unfavorable <a href="/facts/Chemical_equilibrium/y8ToYXHp">chemical equilibrium</a> that must be remedied (e.g. by a large excess of one of the reagents), or by the removal of water (e.g. by using Dean–Stark distillation or including a <a href="/facts/Desiccant/wD2YIcPc">drying agent</a> such as <a href="/facts/Anhydrous/A7B0fDLE">anhydrous</a> salts, <a href="/facts/Molecular_sieve/Lzle8J7k">molecular sieves</a>, or a large amount of certain acids as catalyst in the reaction mixture).

Fischer–Speier esterification open-in-new

Fischer–Speier esterification