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The primary advantages of Fischer esterification compared to other esterification processes are based on its relative simplicity. Straightforward acidic conditions can be used if acid-sensitive functional groups are not an issue; sulfuric acid can be used; weaker acids can be used with a tradeoff of longer reaction times.
Fischer glycosidation (or Fischer glycosylation) refers to the formation of a glycoside by the reaction of an aldose or ketose with an alcohol in the presence of an acid catalyst. The reaction is named after the German chemist, Emil Fischer, winner of the Nobel Prize in chemistry, 1902, who developed this method between 1893 and 1895. [1] [2] [3]
In acid-catalyzed Fischer esterification, the proton binds to oxygens and functions as a Lewis acid to activate the ester carbonyl (top row) as an electrophile, and converts the hydroxyl into the good leaving group water (bottom left). Both lower the kinetic barrier and speed up the attainment of chemical equilibrium.
The mechanism of acid-catalyzed hydrolysis of esters is the reverse of Fischer esterification. Acid is only required in catalytic amounts, as in Fischer esterification, and an excess of water drives the equilibrium towards carboxylic acid and alcohol.
The classic synthesis is the Fischer esterification, which involves treating a carboxylic acid with an alcohol in the presence of a dehydrating agent: RCO 2 H + R'OH ⇌ RCO 2 R' + H 2 O. The equilibrium constant for such reactions is about 5 for typical esters, e.g., ethyl acetate. [15] The reaction is slow in the absence of a catalyst.
The classic example of a dehydration reaction is the Fischer esterification, which involves treating a carboxylic acid with an alcohol to give an ester RCO 2 H + R′OH ⇌ RCO 2 R′ + H 2 O. Often such reactions require the presence of a dehydrating agent, i.e. a substance that reacts with water.
Ethyl propionate can be synthesized by the Fischer esterification of ethanol and propionic acid: CH 3 CH 2 OH + CH 3 CH 2 CO 2 H → CH 3 CH 2 O 2 CCH 2 CH 3 + H 2 O. It participates in condensation reactions by virtue of the weakly acidic methylene group. [7]
A common method for preparing isobutyl acetate is Fischer esterification, where precursors isobutyl alcohol and acetic acid are heated in the presence of a strong acid. Isobutyl acetate has three isomers: n-butyl acetate, tert-butyl acetate, and sec-butyl acetate, which are also common solvents.