Everything about Ethyl Acetate totally explained
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Ethyl acetate (
systematically, ethyl ethanoate, commonly abbreviated
EA) is the
organic compound with the formula CH
3COOCH
2CH
3. This colorless liquid has a characteristic, not unpleasant smell (similar to
pear drops) like certain
glues or
nail polish removers, in which it's used. Ethyl acetate is the
ester from
ethanol and
acetic acid; it's manufactured on a large scale for use as a solvent.
Properties
Ethyl acetate is a moderately polar solvent that has the advantages of being
volatile, relatively non-toxic, and non-
hygroscopic. It is a weak
hydrogen bond acceptor, and isn't a donor due to the lack of an
acidic proton (one directly bonded to an
electronegative atom such as fluorine, oxygen, or nitrogen). Ethyl acetate can dissolve up to 3%
water and has a
solubility of 8% in water at room temperature. At elevated temperature its
solubility in water is higher. It is unstable in the presence of strong aqueous
bases and
acids.
Preparation
Ethyl acetate is synthesized via the
Fischer esterification reaction from
acetic acid and
ethanol, typically in the presence of an acid catalyst such as
sulfuric acid.
» CH
3CH
2OH + CH
3COOH → CH
3COOCH
2CH
3 +
H2O:
It can also be prepared through
Tishchenko reaction, by combining two equivalents of
acetaldehyde in the precence of an
alkoxide base as catalyst. This way is a commercial method of producing ethyl acetate.
» CH
3CHO + CH
3CHO → CH
3COOC
2H
5
Industrial production
Industrially, ethyl acetate can be produced by the catalytic
dehydrogenation of
ethanol. For cost reasons, this method is primarily applied to conversion of surplus ethanol feedstock as opposed to predetermined generation on an industrial scale. In addition, it's commonly accepted as far less practical and less cost effective.
Catalysts for dehydrogenation include copper, operating at an elevated temperature but below 250 °C. The copper may have its surface area increased by depositing it on zinc, promoting the growth of snowflake, fractal like, structures. This surface area can be again increased by deposition onto a
zeolite, typically ZSM-5. Traces of rare earth metals or alkalies, such as that of sodium and potassium, have also been found to be beneficial to the process. Byproducts of hydrogenation include
diethyl ether (thought to primarily arise due to aluminum sites in the catalyst), acetaldehyde, acetaldehyde aldol products, higher esters and ketones.
Acetaldehyde and
MEK complicate conversion and purification as ethanol forms an
azeotrope with water, as does ethyl acetate with ethanol and water and MEK with both ethanol and the acetate. To obtain a high purity product, these azeotropes must be "broken", and this can be achieved by making use of pressure swing distillation.
The composition of the distillate removed from the conversion products is biased towards acetate at atmospheric pressure and ethanol at increased pressure. First, the raw product is fed into a high pressure column where the bulk of the contaminating ethanol is removed. By then feeding the ethanol depleted distillate into a low pressure column, the acetate can be removed from the remaining ethanol azeotrope.
MEK forms during the conversion process from 2-butanol. The latter fails to form an azeotrope with the acetate and so MEK can be removed by hydrogenation of the contaminated product over nickel and further distillation to strip away 2-butanol. This provides the simultaneous benefit of removing the acetylaldehyde contaminant by returning it to an ethanol form and is easily accomplished as hydrogen is a byproduct of the initial dehydrogenation process.
It may also be possible to break the azeotropes with the use of membrane distillation, molecular sieves, an entrainer or absorption medium.
The distilled ethanol and rehydrogenated contaminants can then be recycled into the raw feedstock.
Uses
Solvent
Ethyl acetate is primarily used as a
solvent. For example, it's commonly used to dissolve the pigments for
nail varnishes, and is responsible for the solvent-effect of some nail varnish remover (
acetone and
acetonitrile are also used). Industrially it's used to
decaffeinate coffee beans and tea leaves. It is also used in paints as an activator or hardener.
In the laboratory, a mixture of ethyl acetate and hexane is the most common solvent system used as a
chromatography solvent. It is also used as a solvent for
extractions. It is rarely used as a reaction mixture because it's prone to
hydrolysis.
Like most simple esters, ethyl acetate has a fruity smell. Ethyl acetate is present in confectionery, perfumes, and fruits. In perfumes, it evaporates quickly, leaving but the scent of the perfume on the skin.
Occurrence in wines
Ethyl acetate is present in wines. It may be considered a contaminant at too high concentrations, as typically occurs when wine is exposed to air for a prolonged period. When present at too high concentration in
wine, it's regarded as an off-flavor.
Other uses
In the field of
entomology, ethyl acetate is an effective poison for use in
insect collecting and study. In a
killing jar charged with ethyl acetate, the vapors will kill the collected (usually adult) insect quickly without destroying it. Because it isn't
hygroscopic, ethyl acetate also keeps the insect soft enough to allow proper mounting suitable for a collection.
Reactions
Ethyl acetate can be
hydrolyzed in acid or basic conditions to regain acetic acid and ethanol. The use of an acid catalyst such as
sulfuric acid gives poor yields due to it being an equilibrium — the reverse reaction of the Fischer esterification.
To obtain high yields, it's preferable to use a stoichiometric amount of strong base, such as
sodium hydroxide. This reaction gives ethanol and
sodium acetate, which isn't able to react with ethanol any longer:
» CH
3CO
2C
2H
5 + NaOH → C
2H
5OH + CH
3CO
2Na
Further Information
Get more info on 'Ethyl Acetate'.
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