Ether
| Infobox on Ether | |
|---|---|
| Example of Ether |  |
| Facts | |
| Origin | - |
| Stowage factor (in m3/t) | 1,76 m3/t (drums) |
| Humidity / moisture | - |
| Ventilation | - |
| Risk factors | See text |
Ether
Description
Ether is a class of organic compounds in which an oxygen atom is interposed between two carbon atoms (organic groups) in the molecular structure giving the generic formula ROR. They may be derived from alcohols by elimination of water, but the major method is catalytic hydration of olefins. Only the lowest member of the series, methyl ether, is gaseous; most are liquid and the highest members are solid (cellulose ethers). The term ‘ether’ is often used synonymously with ‘ethyl ether’ and is the legal label name for it.
Ethers are a class of organic compounds that contain an ether group — an oxygen atom connected to two alkyl or aryl groups — of general formula R–O–R'. A typical example is the solvent and anesthetic diethyl ether, commonly referred to simply as "ether" (CH3-CH2-O-CH2-CH3). Ethers are common in organic chemistry and pervasive in biochemistry, as they are common linkages in carbohydrates and lignin.
The names for simple ethers (i.e. those with none or few other functional groups) are a composite of the two substituents followed by "ether." Ethyl methyl ether (CH3OC2H5), diphenylether (C6H5OC6H5). IUPAC rules are often not followed for simple ethers. As for other organic compounds, very common ethers acquired names before rules for nomenclature were formalized. Diethyl ether is simply called "ether," but was once called sweet oil of vitriol. Methyl phenyl ether is anisole, because it was originally found in aniseed. The aromatic ethers include furans. Acetals (α-alkoxy ethers R-CH(-OR)-O-R) are another class of ethers with characteristic properties.
In the IUPAC nomenclature system, ethers are named using the general formula "alkoxyalkane", for example CH3-CH2-O-CH3 is methoxyethane. If the ether is part of a more complex molecule, it is described as an alkoxy substituent, so -OCH3 would be considered a "methoxy-" group. The simpler alkyl radical is written in front, so CH3-O-CH2CH3 would be given as methoxy(CH3O)ethane(CH2CH3). The nomenclature of describing the two alkyl groups and appending "ether", e.g. "ethyl methyl ether" in the example above, is a trivial usage.
Polyethers
Polyethers are compounds with more than one ether group.
The crown ethers are examples of low-molecular weight polyethers. Some toxins produced by dinoflagellates such as brevetoxin and ciguatoxin are in a class known as cyclic or ladder polyethers.
Polyether generally refers to polymers which contain the ether functional group in their main chain. The term glycol is reserved for low to medium range molar mass polymer when the nature of the end-group, which is usually a hydroxyl group, still matters. The term "oxide" or other terms are used for high molar mass polymer when end-groups no longer affect polymer properties.
Ether molecules cannot form hydrogen bonds with each other, resulting in relatively low boiling points compared to those of the analogous alcohols. The difference, however, in the boiling points of the ethers and their isometric alcohols becomes lower as the carbon chains become longer, as the van der Waals interactions of the extended carbon chain dominates over the presence of hydrogen bonding.
Ethers are slightly polar. The C-O-C bond angle in the functional group is about 110°, and the C-O dipoles do not cancel out. Ethers are more polar than alkenes but not as polar as alcohols, esters, or amides of comparable structure. However, the presence of two lone pairs of electrons on the oxygen atoms makes hydrogen bonding with water molecules possible.
Cyclic ethers such as tetrahydrofuran and 1,4-dioxane are miscible in water because of the more exposed oxygen atom for hydrogen bonding as compared to aliphatic ethers.
Application
Organic synthesis, smokeless powder, industrial solvent (nitrocellulose, alkaloids, fats, waxes, etc.); analytical chemistry, anesthetic, extractant.
Diethyl ether is particularly important as a solvent in the production of cellulose plastics such as cellulose acetate and was once used as a general anesthetic.
Diethyl ether has a high cetane number of 85-96 and is used as a starting fluid, in combination with petroleum distillates for gasoline and diesel engines because of its high volatility and low flash point. For the same reason it is also used as a component of the fuel mixture for carbureted compression ignition model engines.
Diethyl ether is a common laboratory solvent. It has limited solubility in water (6.05 g/100 mL at 25°C.) and dissolves 1.5 g/100 mL water at 25°C. Therefore, it is commonly used for liquid-liquid extraction. When used with an aqueous solution, the organic layer is on top as the diethyl ether has a lower density than the water. It is also a common solvent for the Grignard reaction in addition to other reactions involving organometallic reagents. Due to its application in the manufacturing of illicit substances, it is listed in the Table II precursor under the United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances.
Anesthetic use
Diethyl ether depresses the myocardium and increases tracheobronchial secretions.
Diethyl ether could also be mixed with other anesthetic 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. Diethyl ether was found to have many undesirable side effects, such as post-anesthetic nausea and vomiting. Modern anesthetic agents, such as methyl propyl ether (Neothyl) and methoxyflurane (Penthrane) reduce these side effects.
Shipment / Storage
Usually packed in small metal cans or bottles with stoppers. Metal cans usually have metal stoppers secured by means of solder. The stoppers are liable to be jarred loose during transit. In which case lables may be found to be stained and part of the original fluid content lost due to seepage and evaporation.
When packed in bottles with press caps, vapour may escape, although the cap may have the appearance of being quite secure. Sometimes bottles have glass stoppers and paper caps tied with string and dipped in wax. When stowed out of the upright position the stoppers may become loose, allowing the contents to melt the wax, which may give rise to loss due to evaporation.
Also shipped in metal drums (Diethyl ether).
Ether is a colourless, volatile, mobile liquid. Hygroscopic, aromatic odour, burning and sweet taste. The product is soluble in alcohol, chloroform, benzene, solvent naphtha and oils; slightly soluble in water.
Boiling point: 34,5°C
Flashpoint: -116,2°C
Autoignition temperature: 180°C
Store in a segregated and approved area. Keep container in a cool, well-ventilated area. Keep container tightly closed and sealed until ready for use. Avoid all possible sources of ignition (spark or flame). Do not store above 30°C. Hygroscopic; keep container tightly closed. Air Sensitive. Sensitive to light.
Risk factors
Central nervous system depressant by inhalation and skin absorption. Very flammable, severe fire and explosion hazard when exposed to heat or flame.
For overseas carriage aspects of Chemicals, the readers are recommended to acquire or have access to a good chemical dictionary, a copy of the Carriage of Dangerous Goods in Ships, commonly known as the ‘Blue Book’, issued by the Department of Transport, and a copy of the International Maritime Dangerous Goods (IMDG) Code, issued by the International Maritime Organisation. Also consult the applicable MSDS sheet.