Ethyl acetate

Ethyl acetate
IUPAC name
Ethyl acetate
Systematic name
Ethyl ethanoate
Other names
Ethyl ester
Acetic ester
Ester of ethanol
Identifiers
CAS number 141-78-6 YesY
RTECS number AH5425000
Properties
Molecular formula C4H8O2
Molar mass 88.105 g/mol
Appearance colorless liquid
Density 0.897 g/cm³, liquid
Melting point

−83.6 °C, 190 K, -118 °F
Boiling point

77.1 °C, 350 K, 171 °F
Solubility in water 8.3 g/100 mL (20 °C)
Solubility in ethanol,
acetone, diethyl ether,
benzene		 Miscible
Refractive index (nD) 1.3720
Viscosity 0.426 cP at 25 °C
Structure
Dipole moment 1.78 D
Hazards
R-phrases R11, R36, R66, R67
S-phrases S16, S26, S33
NFPA 704
NFPA 704.svg
4
2
0
Flash point −4 °C
LD50 11.3 g/kg, rat
Related compounds
Related carboxylate esters Methyl acetate,
Propyl acetate,
Butyl acetate
Related compounds Acetic acid,
ethanol
 YesY (what is this?)  (verify)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Ethyl acetate (systematically, ethyl ethanoate, commonly abbreviated EtOAc or EA) is the organic compound with the formula CH3COOCH2CH3. This colorless liquid has a characteristic sweet smell (similar to pear drops) like certain glues or nail polish removers, in which it is used. Ethyl acetate is the ester of ethanol and acetic acid; it is manufactured on a large scale for use as a solvent. In 1985, about 400,000 tons were produced yearly in Japan, North America, and Europe combined.[1] In 2004, an estimated 1.3M tons were produced worldwide.[2]

Contents

Production

Ethyl acetate is synthesized industrially mainly via the classic Fischer esterification reaction of ethanol and acetic acid. This mixture converts to the ester in about 65% yield at room temperature:

CH3CH2OH + CH3COOH ⇌ CH3COOCH2CH3 + H2O

The reaction can be accelerated by acid catalysis and the equilibrium can be shifted to the right by removal of water. It is also prepared industrially using the Tishchenko reaction, by combining two equivalents of acetaldehyde in the presence of an alkoxide catalyst:

2 CH3CHO → CH3COOCH2CH3

By dehydrogenation of ethanol

A specialized industrial route entails the catalytic dehydrogenation of ethanol. This method is less cost effective than the esterification but is applied with surplus ethanol in a chemical plant. Typically dehydrogenation is conducted with copper 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 (dendrites). Surface area can be again increased by deposition onto a zeolite, typically ZSM-5. Traces of rare earth and alkali metals are beneficial to the process. Byproducts of the dehydrogenation include diethyl ether, which is thought to primarily arise due to aluminum sites in the catalyst; acetaldehyde and its aldol products; higher esters; and ketones. Separations of the byproducts is complicated by the fact that ethanol forms an azeotrope with water, as does ethyl acetate with ethanol and water, and methyl ethyl ketone (MEK, which forms from 2-butanol) with both ethanol and ethyl acetate. These azeotropes are "broken" by pressure swing distillation or membrane distillation.

Uses

Ethyl acetate is primarily used as a solvent and diluent, being favored because of its low cost, low toxicity, and agreeable odor. For example, it is commonly used to clean circuit boards and in some nail varnish removers (acetone and acetonitrile are also used). Coffee beans and tea leaves are decaffeinated with this solvent.[3] It is also used in paints as an activator or hardener. Ethyl acetate is present in confectionery, perfumes, and fruits. In perfumes, it evaporates quickly, leaving only the scent of the perfume on the skin.

Laboratory uses

In the laboratory, mixtures containing ethyl acetate are commonly used in column chromatography and extractions. Ethyl acetate is rarely selected as a reaction solvent because it is prone to hydrolysis and transesterification.

Ethyl acetate is very volatile and has a low boiling point. Due to these properties, it can be removed from a sample by heating the sample in a hot water bath and providing ventilation with compressed air.

Occurrence in wines

Ethyl acetate is the most common ester in wine, being the product of the most common volatile organic acid — acetic acid, and the ethyl alcohol generated during the fermentation. The aroma of ethyl acetate is most vivid in younger wines and contributes towards the general perception of "fruitiness" in the wine. Sensitivity varies, with most people having a perception threshold around 120 mg/L. Excessive amounts of ethyl acetate are considered a wine fault. Exposure to oxygen can exacerbate the fault due to the oxidation of ethanol to acetaldehyde, which leaves the wine with a sharp vinegar-like taste.[4]

Other uses

In the field of entomology, ethyl acetate is an effective asphyxiant 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 is not hygroscopic, ethyl acetate also keeps the insect soft enough to allow proper mounting suitable for a collection.

Reactions

Ethyl acetate can be hydrolyzed in acidic or basic conditions to regain acetic acid and ethanol. The use of an acid catalyst accelerates the hydrolysis, which is subject to the Fischer equilibrium mentioned above. In the laboratory, and usually for illustrative purposes only, ethyl esters are typically hydrolyzed in a two step process starting with a stoichiometric amount of strong base, such as sodium hydroxide. This reaction gives ethanol and sodium acetate, which is unreactive toward ethanol:

CH3CO2C2H5 + NaOH → C2H5OH + CH3CO2Na

Safety

The LD50 for rats is 11.3 g/kg, indicating low toxicity.[1]

References

  1. ↑ 1.0 1.1 Wilhelm Riemenschneider, Hermann M. Bolt "Esters, Organic" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005. DOI: 10.1002/14356007.a09_565.pub2. Article Online Posting Date: April 30, 2005
  2. ↑ Dutia, Pankaj (August 10th, 2004). "Ethyl Acetate: A Techno-Commercial Profile" (PDF). Chemical Weekly: 184. http://www.chemicalweekly.com/Profiles/Ethyl_Acetate.pdf#page=6. Retrieved 2009-03-21. 
  3. ↑ Folgers.com [1]
  4. ↑ J. Robinson (ed) "The Oxford Companion to Wine" Third Edition pg 259 Oxford University Press 2006 ISBN 0198609906

External links