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  Ethers and Epoxides, Chemistry tutorial

Introduction:

Ethers are the family of organic compounds by the general formula, CnH2n +2O. They are isomeric by the aliphatic monohydric alcohols with the general formula CnH2n+1OH. Epoxides are formed whenever an oxygen atom is associated to carbon atoms of a carbon chain making a three membered ring.

Structures of Ethers:

Ethers acquire the structure: R-O-R'. R and R' might be aliphatic or aromatic.

For illustration:

CH3 - O - CH3

Methoxymethane (Dimethyl ether)

CH3 - O - CH2CH3

Methoxy ethane (Ethyl methyl ether)

Symmetrical and Unsymmetrical Ethers:

Symmetrical ethers are the compounds in which R and R' are similar, they are as well termed as simple ethers.

For illustration:

CH3 - O - CH3            CH3CH2 - O - CH2CH3

Methoxy methane       Ethoxy ethane

Unsymmetrical ethers are the compounds in which R and R' are different, they are as well termed as mixed ethers.

For illustration:

CH3- O- CH2CH3

Methoxyethane

Cyclic Ethers:

These are the compound having the oxygen atom in a ring. They are heterocyclic compounds.

51_Cyclic Ethers.jpg

Fig: Cyclic Ethers

The three membered cyclic ethers are termed as Epoxides. Dissimilar to most ether, Epoxides are extremely reactive substances.

Naming Ethers and Epoxides:

Ethers can be named by using the common system or the IUPAC system.

Common System: In the common system, ethers are named via prefixing the names of alkyl radicals joined to oxygen in alphabetical order prior to the name ether.

For example: CH3-O-CH3 is termed as dimethyl ether and CH3-O-C2H5 is simply ethyl methyl ether (that is, in alphabetical order).

IUPAC System: By using the IUPAC nomenclatures, ethers are termed as alkoxy derivatives of alkanes. The prefix, 'OR' is composed of the name of the simpler alkyl group in the molecule by the '-yl' ending substituted by the '-oxy'. The alkoxy prefix is then followed via the name of the corresponding alkane of the other alkyl group in the molecule.

For illustration:

1196_IUPAC and Common Names of Ethers.jpg

Fig: IUPAC and Common Names of Ethers

In each and every case, the ring is numbered beginning at the oxygen.

Tetrahydropyran and tetrahydrofuran are the acceptable synonyms for oxane and oxalane correspondingly.

Some of the substances have more than one ether linkage, for illustration the diethers, 1, 2-dimethoxyethane and 1, 4-dioxane and the triether, diglyme.

CH3OCH2CH2OCH3           CH3OCH2CH2OCH2CH2OCH3

1, 2-Dimethoxy ethane       Diethylene glycol dimethyl ether

                                                         (Diglyme) 

Compounds that have some ether functions are termed to as polyethers.

Isomerism:

Ethers show the given kinds of structural isomerism.

Functional group isomerism:

Ethers are isomeric with alcohols as both encompass the similar general formula (CnH2n+2O) however different functional groups. For illustration, Methoxymethane (CH3OCH3) and ethanol (CH3CH2OH) have the similar molecular formula, C2H6O.

Metamerism:

Ethers show Metamerism due to the difference in the size of the alkyl groups joined to the oxygen atom. For illustration, the formula C4H10O symbolizes three isomeric ethers or metamers.

CH3OCH2CH2CH3      C2H5OC2H5

Methoxy propane       Ethoxy ethane

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