METHOXYETHANE: STRUCTURE, PROPERTIES, OBTAINING, USES, RISKS - CHEMISTRY - 2025

The methoxyethane is an organic compound of the family of the ethers or alkoxides. Its chemical formula is CH ₃ OCH ₂ CH ₃. It is also called methyl ethyl ether or ethyl methyl ether. It is a gaseous compound at room temperature and its molecule has two methyl groups –CH ₃, one directly attached to oxygen and the other belonging to ethyl –CH ₂ CH ₃.

Methoxyethane is a colorless gas, soluble in water and miscible with ether and ethyl alcohol. Being an ether, it is a low reactive compound, however, it can react at high temperatures with some concentrated acids.

Methoxyethane or methyl ethyl ether. Author: Marilú Stea

It is generally obtained by the so-called Williamson synthesis, which comprises the use of a sodium alkoxide and an alkyl iodide. In turn, its decomposition has been studied under various conditions.

Methoxyethane is used in research laboratories with various objectives, for example, in the study of semiconductor nanomaterials or in the observation of interstellar matter in constellations and large molecular clouds of the universe.

In fact, thanks to very sensitive telescopes (interferometers) it has been detected in certain places in interstellar space.

Structure

The methoxyethane compound has a methyl group -CH ₃ and an ethyl group -CH ₂ CH ₃ both attached to an oxygen.

As can be seen, in this molecule there are two methyl groups, one attached to oxygen CH ₃ -O and the other belonging to ethyl -CH ₂ -CH ₃.

In the ground or lower energy state, the methyl group of –CH ₂ –CH ₃ is in the trans position with respect to the methyl linked to oxygen, that is, in a diametrically opposite place, taking the CH ₂ –O bond as a reference. This is why it is sometimes called trans-ethyl methyl ether.

Structure of trans-ethyl methyl ether in 3D. Black: carbon. White: hydrogen. Red: oxygen. The bond between oxygen and -CH ₂ - can rotate, in which case the two -CH ₃ would be closer to each other. Ben Mills and Jynto. Source: Wikipedia Commons.

This molecule can undergo twisting in the CH ₂ –O bond, which places the methyl in a spatial position different from the trans one, the methyl -CH ₃ groups are very close to each other and this twisting generates an energy transition detectable by instruments sensitive.

Nomenclature

- Methoxyethane.

- Methyl ethyl ether.

- trans-Ethyl methyl ether (mainly in English-speaking literature, translation from English trans - ethyl methyl ether).

Physical properties

Physical state

Colorless gas

Molecular weight

60.096 g / mol

Melting point

-113.0 ºC

Boiling point

7.4 ºC

Flashpoint

1.7 ºC (closed cup method).

Auto-ignition temperature

190 ºC

Specific weight

0.7251 at 0 ºC / 0 ºC (It is less dense than water but heavier than air).

Refractive index

1.3420 at 4 ºC

Solubility

Soluble in water: 0.83 mol / L

Soluble in acetone. Miscible with ethyl alcohol and ethyl ether.

Chemical properties

Methoxyethane is an ether so it is relatively unreactive. The carbon-oxygen-carbon C – O – C bond is very stable against bases, oxidizing and reducing agents. Only its degradation by acids occurs, but this only proceeds under vigorous conditions, that is, with concentrated acids and high temperatures.

However, it tends to oxidize in the presence of air, forming unstable peroxides. If the containers containing it are exposed to heat or fire, the containers explode violently.

Heat decomposition

When methoxyethane is heated between 450 and 550 ° C it decomposes to acetaldehyde, ethane and methane. This reaction is catalyzed by the presence of ethyl iodide, which is generally present in laboratory methoxyethane samples because it is used to obtain it.

Photosensitized decomposition

Methoxyethane irradiated with a mercury vapor lamp (2537 Å wavelength) decomposes generating a wide variety of compounds, among which are: hydrogen, 2,3-dimethoxybutane, 1-ethoxy-2-methoxypropane and methyl vinyl ether.

The final products depend on the irradiation time of the sample, since as the irradiation continues, those that are initially formed later originate new compounds.

By prolonging the irradiation time, the following can also be formed: propane, methanol, ethanol, acetone, 2-butanone, carbon monoxide, ethyl-n-propyl ether and methyl-sec-butyl ether.

Obtaining

Being a non-symmetric ether, methoxyethane can be obtained by the reaction between sodium methoxide CH ₃ ONa and ethyl iodide CH ₃ CH ₂ I. This type of reaction is called Williamson synthesis.

Obtaining methoxyethane by means of the Williamson synthesis. Author: Marilú Stea.

After the reaction is carried out, the mixture is distilled to obtain the ether.

It can also be obtained using sodium ethoxide CH ₃ CH ₂ ONa and methyl sulfate (CH ₃) ₂ SO ₄.

Location in the universe

Trans-ethyl methyl ether has been detected in the interstellar medium in regions such as the Orion constellation KL and in the giant molecular cloud W51e2.

Orion constellation where molecular clouds are observed. Rogelio Bernal Andreo. Source: Wikipedia Commons.

The detection of this compound in interstellar space, together with the analysis of its abundance, is helping to build models of interstellar chemistry.

Uses of methoxyethane

Methoxyethane or methyl ethyl ether is used mostly in laboratory experiments for scientific research.

For studies on interstellar matter

Being an organic molecule with internal rotations, methoxyethane is a chemical compound of interest for studies of interstellar matter.

The internal rotations of its methyl groups produce energy transitions in the microwave region.

Therefore, they can be detected by highly sensitive telescopes such as the Atacama Large Millimeter / submillimeter Array, or ALMA.

Appearance of a part of the great ALMA astronomical observatory. ESO / José Francisco Salgado (josefrancisco.org). Source: Wikipedia Commons.

Thanks to its internal rotation and large space observatories, trans-methyl ethyl ether has been found in the constellation of Orion and in the giant molecular cloud W51e2.

To deduce chemical transformations in various fields of study

Some researchers observed the formation of methoxyethane or methyl ethyl ether when a mixture of ethylene CH ₂ = CH ₂ and methanol CH ₃ OH is irradiated with electrons.

The reaction mechanism goes through the formation of the radical CH ₃ O •, which attacks the double bond rich in electrons of CH ₂ = CH ₂. The resulting CH ₃ -O-CH ₂ -CH ₂ • adduct captures a hydrogen from a CH ₃ OH and forms the methyl ethyl ether CH ₃ -O-CH ₂ -CH ₃.

The study of this type of reactions induced by the irradiation of electrons is useful in the field of biochemistry since it has been determined that they can cause damage to DNA, or in the field of organometallic chemistry since it favors the formation of nanostructures.

Additionally, it is known that large amounts of secondary electrons are produced when electromagnetic or particulate radiation interacts with condensed matter in space.

Therefore, it is estimated that these electrons can initiate chemical transformations in interstellar dust matter. Hence the importance of studying methyl ethyl ether in these reactions.

Potential use in semiconductors

Using computational calculation methods some scientists found that methoxyethane or methyl ethyl ether can be adsorbed by gallium (Ga) doped graphene (note that adsorption is different from absorption).

Graphene is a nanomaterial made up of carbon atoms that are arranged in a hexagonal pattern.

Microscopic view of graphene. Maido Merisalu. Source: Wikipedia Commons.

The adsorption of methoxyethane on doped graphene occurs through the interaction between the oxygen in the ether and the gallium atom on the surface of the nanomaterial. Due to this adsorption there is a net charge transfer from ether to gallium.

After the adsorption of methyl ethyl ether and due to this charge transfer, gallium doped graphene exhibits p-type semiconductor properties.

Risks

Methoxyethane is highly flammable.

When in contact with air it has a tendency to form unstable and explosive peroxides.

References

1. US National Library of Medicine. (2019). Ethyl Methyl Ether. Recovered from: pubchem.ncbi.nlm.nih.gov.
2. Irvine WM (2019) Ethyl Methyl Ether (C ₂ H ₅ OCH ₃). In: Gargaud M. et al. (eds). Encyclopedia of Astrobiology. Springer, Berlin, Heidelberg. Recovered from link.springer.com.
3. Third, B. et al. (2015). Searching for trans ethyl methyl ether in Orion KL. Astronomy & Astrophysics. 582, L1 (2015). Recovered from ncbi.nlm.nih.gov.
4. Filseth, SV (1969). The Mercury 6 (³ P ₁) Photosensitized Decomposition of Methyl Ethyl Ether. The Journal of Physical Chemistry. Volume 73, Number 4, April 1969, 793-797. Recovered from pubs.acs.org.
5. Casanova, J.Jr. (1963). Student Preparation and Manipulation of a Gas-Methyl Ethyl Ether. Journal of Chemical Education. Volume 40, Number 1, January 1963. Recovered from pubs.acs.org.
6. Ure, W. and Young, JT (1933a). On the mechanism of gaseous reactions. I. The thermal decomposition of Methyl Ethyl Ether. The Journal of Physical Chemistry, Vol. XXXVII, No.9: 1169-1182. Recovered from pubs.acs.org.
7. Ure, W. and Young, JT (1933b). On the mechanism of gaseous reactions. II. Homogeneous Catalysis in the Decomposition of Methyl Ethyl Ether. The Journal of Physical Chemistry, 37, 9, 1183-1190. Recovered from pubs.acs.org.
8. Shokuhi Rad, A. et al. (2017). DFT Study on the adsorption of diethyl, ethyl methyl, and dimethyl ethers on the surface of Gallium doped graphene. Applied Surface Science. Volume 401, 15 April 2017, pages 156-161. Recovered from sciencedirect.com.
9. Schmidt, F. et al. (2019). Electron-Induced Formation of Ethyl Methyl Ether in Condensed Mixtures of Methanol and Ethylene. J. Phys. Chem. A 2019, 123, 1, 37-47. Recovered from pubs.acs.org.