Esterification
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Esterification is the general name for a chemical reaction in that an ester is the reaction product.
Esterification reactions include
- the Fischer esterification (refluxing a carboxylic acid and an alcohol in the presence of an acid catalyst) in the absence of water with alcohol/phenole
- the reaction of a carboxylic acid halogenide (which is also called acyl halide) with an alcohol/phenole
- the reaction of a carboxylic anhydride with an alcohol/phenole.
- the reaction of an alkali carboxylate and an alcohol
Examples
- The Fischer esterification of acetic acid in excess ethanol in the presence of sulfuric acid resulting in the ester ethyl acetate.
H3C-COOH + HO-CH2-CH3 + H2SO4 → H3C-COO-CH2-CH3 + H2SO4 + H-0-H
This reaction is the so called tutorial model reaction, which is found in every college-grade tutorial. It is evident and very easy to understand the mechanism of the SN2 (two-phase-nucleophile-substitution) reaction. This reaction works only for special esters and needs much laboratorial skill, because you have to reflux, but to eflux the water, hence the water would lead the reaction to the left side. Besides that, the acidification catalyses the esterification, but in bigger amounts also the hydrolysis. Therefore, it is NOT useful to use sulfuric acid in doses capable to bind the resulting water.
- The reaction of acetyl chloride with ethanol
H3C-COCl + HO-CH2-CH3 → H3C-COO-CH2-CH3 + H-Cl
This reaction is NOT a tutorial reaction, hence it is not very evident. But this reaction is easy to perform, even with basic laboratorial skill.
- The reaction of acetic anhydride with ethanol
H3C-CO-O-CO-CH3 + HO-CH2-CH3 → H3C-COO-CH2-CH3 + H3C-COOH
This reaction is the easiest to perform, although it is rarely cited in tuturials. The reaction has a bigger practical interest: The synthesis of aspirine is performed that way. Pyridine is often used in such reactions as a scavenger for protons.
- The reaction of sodium acetate with ethanol
H3C-COO- Na+ + HO-CH2-CH3 + H+ → H3C-COO-CH2-CH3 + H-0-H
Hence, the reaction runs with sodium acetate in excess, and because sodium acetate binds 3 water molecules, this reaction, I read only once might be possible to be performed.
See also
- Transesterification, a reaction to transform one ester into a different ester.
- Hydrolysis, the cleavage of an ester with water back to a carboxylic acid and alcohol.
- acetylation
- acylation
de:Veresterung es:Esterificación nl:Verestering pl:Estryfikacja zh:酯化