Ether

# Overview
Ether is the general name for a class of chemical compounds which contain an ether group  an oxygen atom connected to two (substituted) alkyl or aryl groups  of general formula R  OR'. A typical example is the solvent and anesthetic diethyl ether, commonly referred to simply as "ether" (ethoxyethane, CH3-CH2-O-CH2-CH3).

# Physical properties
Ether molecules cannot form hydrogen bonds among each other, resulting in a relatively low boiling point comparable to that of the analogous alcohols. However, the differences in the boiling points of the ethers and their isometric alcohols become smaller as the carbon chains become longer, as the hydrophobic nature of the carbon chain becomes more predominant over the presence of hydrogen bonding.
Ethers are slightly polar as the C - O - C bond angle in the functional group is about 110 degrees, and the C - O dipole does 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, causing the solubility of alcohols (for instance, butan-1-ol) and ethers (ethoxyethane) to be quite dissimilar.
Cyclic ethers such as tetrahydrofuran and 1,4-dioxane are totally miscible in water because of the more exposed oxygen atom for hydrogen bonding as compared to aliphatic ethers.
Ethers can act as Lewis bases. For instance, diethyl ether forms a complex with boron compounds, such as boron trifluoride diethyl etherate (BF3.OEt2). Ethers also coordinate to magnesium in Grignard reagents (RMgBr).

# Nomenclature
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(CH3)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.

# Similar structures
Ethers are not to be confused with the following classes of compounds with the same general structure R-O-R.
- Aromatic compounds like furan where the oxygen is part of the aromatic system.
- Compounds where one of the carbon atoms next to the oxygen is connected to oxygen, nitrogen, or sulfur:
Esters R-C(=O)-O-R
Acetals R-CH(-O-R)-O-R
Aminals R-CH(-NH-R)-O-R
Anhydrides R-C(=O)-O-C(=O)-R
- Esters R-C(=O)-O-R
- Acetals R-CH(-O-R)-O-R
- Aminals R-CH(-NH-R)-O-R
- Anhydrides R-C(=O)-O-C(=O)-R

# Primary, secondary, and tertiary ethers
The terms "primary ether", "secondary ether", and "tertiary ether" are occasionally used and refer to the carbon atom next to the ether oxygen. In a primary ether this carbon is connected to only one other carbon as in diethyl ether CH3-CH2-O-CH2-CH3. An example of a secondary ether is diisopropyl ether (CH3)2CH-O-CH(CH3)2 and that of a tertiary ether is di-tert-butyl ether (CH3)3C-O-C(CH3)3.
Dimethyl ether, a primary, a secondary, and a tertiary ether.

# Polyethers
Polyethers are compounds with more than one ether group. While the term generally refers to polymers like polyethylene glycol and polypropylene glycol, low molecular compounds such as the crown ethers may sometimes be included.

# Organic reactions

## Synthesis
Ethers can be prepared in the laboratory in several different ways.
- Intermolecular Dehydration of alcohols:
- Nucleophilic displacement of alkyl halides by alkoxides
- Nucleophilic Displacement of Alkyl halides by phenoxides
- Electrophilic addition of alcohols to alkenes.
Cyclic ethers which are also known as epoxides can be prepared:
- By the oxidation of alkenes with a peroxyacid such as m-CPBA.
- By the base intramolecular nuclephilic substitution of a halohydrin.

## Reactions
Ethers in general are of very low chemical reactivity. Organic reactions are:
- Hydrolysis.
- Nucleophilic displacement.
- Peroxide formation.

# Important ethers