Dimethyl ether

Ball-and-stick Stick Space-filling

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9 atoms, 8 single bonds.

IUPAC name: methoxymethane
Molar mass: 46.0690(62) g/mol
Atoms: 9
SMILES: COC
InChIKey: LCGLNKUTAGEVQW-UHFFFAOYSA-N
PubChem CID: 8254

Made of

Structural formula of dimethyl ether. Every atom in the molecule is drawn. It shows which atoms are joined to which, not the shape. The model above shows the shape.

At room temperature dimethyl ether is a gas, but an easily condensed one, and it travels as a liquid held in by its own vapour pressure. The gas has no colour and a faint ethereal smell, in the description of CAMEO Chemicals, a reference on hazardous materials. ChEBI, the Chemical Entities of Biological Interest database, defines it as an ether whose single oxygen atom is bonded to two methyl groups. A methyl group is one carbon atom carrying three hydrogens. An oxygen bridging two carbons is the mark of every ether in Chem1’s account.

Two carbon atoms, six hydrogen atoms and one oxygen atom add up to C₂H₆O and a molar mass of 46.07 g/mol. The IUPAC name is methoxymethane. Water dissolves a large volume of the gas: one volume of water takes up 37 volumes of it, according to the Hazardous Substances Data Bank (HSDB). Set alight, it burns with a slightly luminous flame.

Structure and bonding

Dimethyl ether has a C, O, C skeleton: the oxygen sits between the two carbons, and each carbon carries three hydrogens. Nine atoms are joined by eight single bonds, two C–O and six C–H, with no ring, double bond or charge anywhere. The molecule is CH₃–O–CH₃ in Chem1’s notation, and the model draws exactly that connectivity. In Ball-and-stick the chain bends at the oxygen. PubChem’s computed model opens the C–O–C angle to 111.5°, with each C–O bond 1.421 Å long and each C–H bond about 1.09 Å.

Each carbon aims its four bonds at the corners of a tetrahedron, as Chem1 describes carbon in most of its organic compounds. Stick view thins the atoms away, leaving a wide V with a tuft of three hydrogens at each tip. In Space-filling the nine atoms pack into one compact body, with the oxygen showing only on the outer side of its bend. Its non-bonding electrons appear in no view, yet the molecule uses them. On Chem1’s account the oxygen offers that pair to an electron-deficient boron atom, which makes dimethyl ether a Lewis base.

Where it turns up

Aerosol sprays have been among the major uses of dimethyl ether, and in cosmetics it works as both a propellant and a solvent. HSDB records it, mixed with water and carbon dioxide, as the carrier for a hair-care product. Products containing it run from personal care and pet care to car products, hobby supplies and home maintenance, according to the Consumer Product Information Database.

Outside the spray can it has served as a refrigerant and a solvent, and it goes into making plastics (HSDB). Welders burn it as a fuel for cutting and brazing metal as well as for welding. HSDB also notes a small food use: meat and fish have been frozen by dipping them directly into it. The Formox process that makes formaldehyde gives it off as a by-product, together with carbon monoxide.

Why it matters

Dimethyl ether and ethanol share one formula, C₂H₆O, and are still two substances. Ethanol is C₂H₅OH and dimethyl ether CH₃–O–CH₃: the same nine atoms, connected in a different order. What a substance is depends on how its atoms are joined, and in Chem1’s account the two connectivities give the pair quite different physical and chemical properties. Their boiling points are compared on the ethanol page. In Chem1’s account organic compounds make the point sharpest, since hundreds or even thousands of molecules can share one empirical formula.

When spray cans gave up CFCs (chlorofluorocarbons), hydrocarbons and a mixture of dimethyl ether with water became the most common replacements as propellant and solvent, according to HSDB. Why the CFCs went is part of the story of ozone. Chemical plants also use it as an extracting agent and as a methylating agent, which attaches methyl groups to other molecules. Over zeolite catalysts it becomes hydrocarbons of two to ten carbons (HSDB). The US Environmental Protection Agency (EPA) puts the national volume for 2023 at 10 million to under 50 million pounds.

Properties

Properties of dimethyl ether Molar mass summed from IUPAC/CIAAW 2024 standard atomic weights; formula, atom and bond counts and PubChem's molecular weight from PubChem CID 8254.
Property	Value	Unit	Source
Molecular formula (Hill order)	C₂H₆O
Molar mass	46.0690(62) g/mol	g/mol	IUPAC/CIAAW 2024
Carbon atoms	2
Hydrogen atoms	6
Oxygen atoms	1
Bonds	8
PubChem molecular weight	46.07 g/mol	g/mol	PubChem

Safety

Dimethyl ether is an extremely flammable gas under pressure, and a heated container of it may explode. Evaporating liquid can cause frostbite, and the gas, heavier than air, can collect low down and leave too little oxygen, according to the International Chemical Safety Card (ICSC). It can form explosive peroxides on standing in air, according to ICSC, CAMEO and HSDB, although HSDB also describes it as not prone to peroxide formation. The PubChem Laboratory Chemical Safety Summary gathers these hazards and the workplace exposure limits set for it.

Questions

What shape is a dimethyl ether molecule?

Dimethyl ether has no one central atom: the oxygen and both carbons each anchor bonds of their own. The C–O–C chain bends at the oxygen, at 111.5° in PubChem's computed model, and every bond in it is single. Around each carbon the computed O–C–H angles run from 108.4° to 110.5°, near the tetrahedral 109.5° that Chem1 gives.

Is dimethyl ether a gas or a liquid?

A gas at ordinary temperatures. The Hazardous Substances Data Bank (HSDB) gives its boiling point as −24.8 °C, and the International Chemical Safety Card gives −23.6 °C. HSDB puts the melting point at −141.5 °C and the vapour at 1.6 times the density of air. Suppliers still handle it as a liquid, kept that way in its container by its own vapour pressure, on CAMEO Chemicals' description.

Is dimethyl ether harmful to breathe?

Breathing it can bring on some anaesthesia, weaker than diethyl ether's, together with blurred vision, headache, intoxication and loss of consciousness, according to CAMEO Chemicals. It may also affect the central nervous system and lower consciousness, according to the International Chemical Safety Card. The gas can also asphyxiate by pushing out the air. Workplace exposure limits exist for it, and PubChem's Laboratory Chemical Safety Summary lists them with the other hazards.

How is dimethyl ether made?

Industry takes water out of methanol over a catalyst, a reaction called catalytic dehydration, and the Hazardous Substances Data Bank notes that laboratories have made it from methanol with acidic catalysts for many years. The very pure grade sold as an aerosol propellant goes through further purification. Some also forms as a by-product of one industrial route to methanol.

Made of the same elements

C₂H₅OH Ethanol 9 atoms, 8 single bonds.
C₃H₆O Acetone 10 atoms, 9 bonds.
C₂H₆O₂ Ethylene glycol 10 atoms, 9 single bonds.
CH₃CHO Acetaldehyde 7 atoms, 6 bonds.
C₂H₄O Ethylene oxide 7 atoms, 7 single bonds.
C₂H₅COOH Propionic acid 11 atoms, 10 bonds.
C₃H₇OH 1-Propanol 12 atoms, 11 single bonds.
CH₃COOH Acetic acid 8 atoms, 7 bonds.

All 51 compounds made of carbon, hydrogen and oxygen

C₃H₈O Isopropyl alcohol 12 atoms, 11 single bonds.
C₃H₆O₃ Lactic acid 12 atoms, 11 bonds.
CH₃OH Methanol 6 atoms, 5 single bonds.
C₄H₈O Butanone 13 atoms, 12 bonds.
C₂H₄O₃ Glycolic acid 9 atoms, 8 bonds.
C₆H₅OH Phenol 13 atoms, 13 bonds.
C₃H₈O₂ Propylene glycol 13 atoms, 12 single bonds.
C₆H₅CHO Benzaldehyde 14 atoms, 14 bonds.
C₃H₇COOH Butyric acid 14 atoms, 13 bonds.
CH₃COOC₂H₅ Ethyl acetate 14 atoms, 13 bonds.
CH₂O Formaldehyde 4 atoms, 3 bonds.
C₃H₈O₃ Glycerol 14 atoms, 13 single bonds.
C₄H₉OH 1-Butanol 15 atoms, 14 single bonds.
C₆H₅COOH Benzoic acid 15 atoms, 15 bonds.
C₂H₅OC₂H₅ Diethyl ether 15 atoms, 14 single bonds.
HCOOH Formic acid 5 atoms, 4 bonds.
C₄H₆O₅ Malic acid 15 atoms, 14 bonds.
H₂CO₃ Carbonic acid 6 atoms, 5 bonds.
H₂C₂O₄ Oxalic acid 8 atoms, 7 bonds.
C₇H₆O₃ Salicylic acid 16 atoms, 16 bonds.
C₄H₆O₆ Tartaric acid 16 atoms, 15 bonds.
C₈H₈O₃ Methyl salicylate 19 atoms, 19 bonds.
C₈H₈O₃ Vanillin 19 atoms, 19 bonds.
C₆H₈O₆ Ascorbic acid 20 atoms, 20 bonds.
C₉H₈O₄ Aspirin 21 atoms, 21 bonds.
C₆H₈O₇ Citric acid 21 atoms, 20 bonds.
C₆H₁₂O₆ Fructose 24 atoms, 24 single bonds.
C₆H₁₂O₆ Glucose 24 atoms, 24 single bonds.
C₁₀H₂₀O Menthol 31 atoms, 31 single bonds.
C₁₄H₁₄O₃ Naproxen 31 atoms, 32 bonds.
C₁₅H₁₆O₂ Bisphenol A 33 atoms, 34 bonds.
C₁₃H₁₈O₂ Ibuprofen 33 atoms, 33 bonds.
C₂₀H₁₄O₄ Phenolphthalein 38 atoms, 41 bonds.
C₁₈H₂₄O₂ Estradiol 44 atoms, 47 bonds.
C₁₂H₂₂O₁₁ Lactose 45 atoms, 46 single bonds.
C₁₂H₂₂O₁₁ Sucrose 45 atoms, 46 single bonds.
C₁₉H₂₈O₂ Testosterone 49 atoms, 52 bonds.
C₁₆H₃₂O₂ Palmitic acid 50 atoms, 49 bonds.
C₂₁H₃₀O₂ Progesterone 53 atoms, 56 bonds.
C₁₈H₃₄O₂ Oleic acid 54 atoms, 53 bonds.
C₂₁H₃₀O₅ Cortisol 56 atoms, 59 bonds.
C₂₇H₄₄O Cholecalciferol 72 atoms, 74 bonds.
C₂₇H₄₆O Cholesterol 74 atoms, 77 bonds.