Ethyl acetate

Organic compound (CH₃CO₂CH₂CH₃)

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Chemical compound

Ethyl acetate (systematically ethyl ethanoate, commonly abbreviated as EtOAc, ETAC, or EA) is an organic compound with the formula CH₃CO₂CH₂CH₃, simplified to C₄H₈O₂. This flammable, colorless liquid has a distinctive sweet smell, similar to pear drops. It is commonly used in glues, nail polish removers, and the decaffeination processes for tea and coffee. Ethyl acetate is the ester of ethanol and acetic acid and is produced on a large scale for use as a solvent.

Production and Synthesis

Ethyl acetate was first synthesized by Count de Lauraguais by distilling a mixture of ethanol and acetic acid.

In 2020, an estimated 1.3 million tonnes were produced worldwide. The combined annual production in Japan, North America, and Europe was approximately 400,000 tonnes. The global ethyl acetate market was valued at $3.3 billion in 2020.

Ethyl acetate is primarily synthesized in the industry via the classic Fischer esterification reaction between ethanol and acetic acid. This method yields the ester at about 65% efficiency at room temperature:

CH₃CO₂H + CH₃CH₂OH → CH₃CO₂CH₂CH₃ + H₂O

The reaction can be accelerated through acid catalysis, and the equilibrium can be shifted to favor ester production by removing water.

Another industrial method involves the Tishchenko reaction, which combines two equivalents of acetaldehyde in the presence of an alkoxide catalyst:

2 CH₃CHO → CH₃CO₂CH₂CH₃

Silicotungstic acid can also be used to manufacture ethyl acetate by the alkylation of acetic acid with ethylene:

C₂H₄ + CH₃CO₂H → CH₃CO₂C₂H₅

Uses

Ethyl acetate is primarily used as a solvent and diluent due to its low cost, low toxicity, and pleasant odor. It is frequently used to clean circuit boards and is found in some nail varnish removers (acetone is also used). This solvent is utilized to decaffeinate coffee beans and tea leaves. Additionally, it serves as an activator or hardener in paints, and it appears in confectionery, perfumes, and fruits; in perfumes, it evaporates quickly, leaving the scent on the skin.

Insect collectors use ethyl acetate as an asphyxiant. When used in a killing jar, the vapors effectively kill collected insects without damaging them. Since it is not hygroscopic, ethyl acetate maintains the insect's softness for proper mounting; however, it may potentially harm insect DNA, making specimens less suitable for subsequent DNA sequencing.

Laboratory Uses

In laboratory settings, mixtures containing ethyl acetate are commonly employed in column chromatography and extractions. However, it is rarely chosen as a reaction solvent because it is susceptible to hydrolysis, transesterification, and condensation reactions.

Occurrence in Wines

Ethyl acetate is the most prevalent ester in wine, formed from acetic acid and ethyl alcohol generated during fermentation. Its aroma is particularly notable in younger wines, contributing to the overall perception of "fruitiness." Most individuals have a perception threshold around 120 mg/L, and excessive amounts of ethyl acetate are considered a fault in wine.

Reactions

Ethyl acetate exhibits weak Lewis basic properties, similar to typical carboxylic acid esters. It hydrolyzes to yield acetic acid and ethanol, with bases accelerating this hydrolysis. In laboratories, ethyl esters are often hydrolyzed as part of a two-step process, beginning with a strong base such as sodium hydroxide:

CH₃CO₂C₂H₅ + NaOH → C₂H₅OH + CH₃CO₂Na

In the Claisen condensation reaction, anhydrous ethyl acetate reacts with strong bases to produce ethyl acetoacetate.

Properties

Physical Properties

Under normal conditions, ethyl acetate is a colorless, low-viscosity, and flammable liquid. Its melting point is -83 °C, with a melting enthalpy of 10.48 kJ/mol. At atmospheric pressure, it boils at 77 °C, with a vaporization enthalpy of 31.94 kJ/mol. The vapor pressure adheres to the Antoine equation:

log₁₀ (p) = A - B/(T + C)

This relationship is valid within the temperature range of 289 to 349 K (16 to 76 °C).

The enthalpy of vaporization can be calculated using the empirical equation:

ΔH_vap = A exp(-β T_r) (1 - T_r)^β

This function summarizes the critical thermodynamic properties of ethyl acetate under various conditions.

Safety

The LD50 for rats is 5000 mg/kg, indicating low acute toxicity. Given that ethyl acetate is naturally present in many organisms, the risk of toxicity is minimal.

Overexposure may lead to irritation of the eyes, nose, and throat. Severe cases may induce weakness, drowsiness, or unconsciousness. Concentrations as low as 400 ppm can cause irritation. While ethyl acetate is an irritant, its effects are milder compared to propyl acetate or butyl acetate.

References