Diethyl ether

Diethyl ether
Skeletal formula
Ball-and-stick model
IUPAC name Ethoxyethane
Other names Diethyl ether; Ethyl ether; Ethyl oxide; 3-Oxapentane; Ethoxyethane
style="background: #F8EABA; text-align: center;" colspan="2" | Identifiers
CAS number	60-29-7 Y
PubChem	3283
ChemSpider	3168
RTECS number	KI5775000
SMILES
InChI
InChI key	RTZKZFJDLAIYFH-UHFFFAOYAB
style="background: #F8EABA; text-align: center;" colspan="2" | Properties
Molecular formula	C4H10O
Molar mass	74.12 g mol−1
Appearance	Colorless liquid
Density	0.7134 g/cm3, liquid
Melting point	-116.3 °C, 157 K, -177 °F
Boiling point	34.6 °C, 308 K, 94 °F
Solubility in water	6.9 g/100 ml (20 °C)
Viscosity	0.224 cP (25 °C)
style="background: #F8EABA; text-align: center;" colspan="2" | Structure
Dipole moment	1.15 D (gas)
style="background: #F8EABA; text-align: center;" colspan="2" | Hazards
MSDS	External MSDS
R-phrases	R12 R19 R20 R22 R66 R67
S-phrases	S9 S16 S29 S33
NFPA 704	75px 4 2 1
Flash point	-45 °C
Autoignition temperature	160 °C
style="background: #F8EABA; text-align: center;" colspan="2" | Related compounds
Related Ethers	Dimethyl ether Methoxypropane
Related compounds	Diethyl sulfide
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Diethyl ether, also known simply as ether, is the organic compound with the formula (C₂H₅)₂O. It is a colorless and highly flammable liquid with a low boiling point and a characteristic odor. It is the most common member of a class of chemical compounds known generically as ethers. It is a common solvent and was once used as a general anesthetic. Ether is sparingly soluble in water (6.9 g/100 mL).

History

Alchemist Raymundus Lullus is credited with discovering the compound in AD 1275, although there is no contemporary evidence of this. It was first synthesized in 1540 by Valerius Cordus, who called it "sweet oil of vitriol" (oleum dulce vitrioli) — the name reflects the fact that it is obtained by distilling a mixture of ethanol and sulfuric acid (then known as oil of vitriol)—and noted some of its medicinal properties. At about the same time, Theophrastus Bombastus von Hohenheim, better known as Paracelsus, discovered ether's analgesic properties. The name ether was given to the substance in 1730 by August Siegmund Frobenius.

Metabolism

A cytochrome P450 enzyme is proposed to metabolize diethyl ether.

Diethyl ether inhibits alcohol dehydrogenase, and thus slows the metabolism of ethanol. It also inhibits metabolism of other drugs requiring oxidative metabolism.

Applications

It is particularly important as a solvent in the production of cellulose plastics such as cellulose acetate.

As a fuel

Diethyl ether has a high cetane number of 85 - 96 and is used as a starting fluid for diesel and gasoline engines because of its high volatility and low autoignition temperature. For the same reason it is also used as a component of the fuel mixture for carbureted compression ignition model engines.

Laboratory uses

Diethyl ether is a common laboratory solvent. It has limited solubility in water, thus it is commonly used for liquid-liquid extraction. Being less dense than water, the ether layer is usually on top. Diethyl ether is a common solvent for the Grignard reaction, and for many other reactions involving organometallic reagents. Due to its immiscibility with water and the fact that non-polar organic compounds are highly soluble in it, ether is also used in the production of freebase cocaine, and is listed as a Table II precursor under the United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances. However, for that purpose it has been largely replaced by cheaper, safer, uncontrolled hydrocarbons.

Anesthetic use

File:Ether monument-Boston.JPG

Panel from monument in Boston commemorating Morton's demonstration of ether's anesthetic use.

William T.G. Morton participated in a public demonstration of ether anesthesia on October 16, 1846 at the Ether Dome in Boston, Massachusetts. However, Crawford Williamson Long, M.D., is now known to have demonstrated its use privately as a general anesthetic in surgery to officials in Georgia, as early as March 30, 1842, and Long publicly demonstrated ether's use as a surgical anesthetic on numerous occasions before 1846.

Ether was sometimes used in place of chloroform because it had a higher therapeutic index, a larger difference between the recommended dosage and a toxic overdose. Ether is still the preferred anesthetic in some developing nations due to its high therapeutic index (~1.5-2.2) and low price. Because of its associations with Boston, the use of ether became known as the "Yankee Dodge."

Ether could also be mixed with other anaesthetic agents such as chloroform to make C.E. mixture, or chloroform and alcohol to make A.C.E. mixture.

Today, ether is rarely used. The use of flammable ether was displaced by nonflammable anesthetics such as halothane. Additionally, ether had many undesirable side effects, such as postanesthetic nausea and vomiting. Modern anesthetic agents, such as methyl propyl ether (Neothyl) and methoxyflurane (Penthrane) reduce these side effects.

Recreational use

See also: Addiction to ether consumption

The anesthetic effects of ether have made it a recreational drug, although not a popular one. Diethyl ether is not as toxic as other solvents used as recreational drugs.

Ether, mixed with ethanol, was marketed in the 19th century as a cure-all and recreational drug, during one of Western society's temperance movements. At the time, it was considered improper for women to consume alcoholic beverages at social functions, and sometimes ether-containing drugs would be consumed instead. A cough medicine called Hoffmann's Drops was marketed at the time as one of these drugs, and contained both ether and alcohol in its capsules. Ether tends to be difficult to consume alone, and thus was often mixed with drugs like ethanol for recreational use. Ether may also be used as an inhalant.

In the 19th century and early 20th century ether drinking was popular among Polish peasants . It is a traditional and still relatively popular recreational drug among Lemkos. It is usually consumed in a small quantity (kropka, or “dot”) poured over milk, water with sugar or orange juice in a shot glass.

Production

Most diethyl ether is produced as a byproduct of the vapor-phase hydration of ethylene to make ethanol. This process uses solid-supported phosphoric acid catalysts and can be adjusted to make more ether if the need arises. Vapor-phase dehydration of ethanol over some alumina catalysts can give diethyl ether yields of up to 95%.

Diethyl ether can be prepared both in laboratories and on an industrial scale by the acid ether synthesis. Ethanol is mixed with a strong acid, typically sulfuric acid, H₂SO₄. The acid dissociates producing hydrogen ions, H⁺. A hydrogen ion protonates the electronegative oxygen atom of the ethanol, giving the ethanol molecule a positive charge:

CH₃CH₂OH + H⁺ → CH₃CH₂OH₂⁺

A nucleophilic oxygen atom of unprotonated ethanol displaces a water molecule from the protonated (electrophilic) ethanol molecule, producing water, a hydrogen ion and diethyl ether.

CH₃CH₂OH₂⁺ + CH₃CH₂OH → H₂O + H⁺ + CH₃CH₂OCH₂CH₃

This reaction must be carried out at temperatures lower than 150 °C in order to ensure that an elimination product (ethylene) is not a product of the reaction. At higher temperatures, ethanol will dehydrate to form ethylene. The reaction to make diethyl ether is reversible, so eventually an equilibrium between reactants and products is achieved. Getting a good yield of ether requires that ether be distilled out of the reaction mixture before it reverts to ethanol, taking advantage of Le Chatelier's principle.

Another reaction that can be used for the preparation of ethers is the Williamson ether synthesis, in which an alkoxide (produced by dissolving an alkali metal in the alcohol to be used) performs a nucleophilic substitution upon an alkyl halide.

Safety

Diethyl ether is prone to peroxide formation, and can form explosive diethyl ether peroxide. Ether peroxides are higher boiling and are contact explosives when dry. Diethyl ether is typically supplied with trace amounts of the antioxidant BHT (2,6-di-tert-butyl-4-methylphenol), which reduces the formation of peroxides. Storage over NaOH precipitates the intermediate ether hydroperoxides. Water and peroxides can be removed by either distillation from sodium and benzophenone, or by passing through a column of activated alumina.

Ether is extremely flammable. The autoignition temperature of ether is only 170 °C (338°F), so it can be ignited by a hot surface without a flame or spark. A common practice in chemical labs is to use steam (thus limiting the temperature to 100 °C (212 °F) when ether must be heated or distilled. The diffusion of diethyl ether in air is 0.918·10⁻⁵ m²/s (298K 101.325 kPa).

External links

• Erowid.org
• Michael Faraday's announcement of ether as an anesthetic in 1818
• The unusual history of ether as an anesthetic, anesthesia-nursing.com
• Etheromania, worldwidewords.org
• Calculation of vapor pressure, liquid density, dynamic liquid viscosity, surface tension of diethyl ether, ddbonline.ddbst.de

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