Ethers
Ethers are the class of Organic Compounds in which the alkyl groups are linked to each other with an Oxygen atom. In organic chemistry, Ethers are derived from alcohols. If hydrogen is replaced by an alkyl or aryl group then there is a new class of compounds formed known as ethers.
In this article, we will learn what Ether is, what is structure of Ether, how to do the Nomenclature of Ether, what are the physical and chemical properties of Ether, and the distinction between Ether and Ester in detail.
Table of Content
- What is Ether?
- Structure of Ethers
- IUPAC Naming of Ethers
- Types of Ethers
- Synthesis of Ethers
- Esters and Ethers
What is Ether?
In organic chemistry, Ethers are compounds having an oxygen atom in the center connected with two alkyl or aryl groups on both sides of the oxygen atom. They have the general formula R−O−R′, where R and R′ represent the alkyl or aryl groups. Both R and R’ may be the same or different.
Ethers may also be defined as derivatives of hydrocarbons in which a hydrogen atom is replaced by an alkoxy (-OR) or aryloxy (- OAr) group.
The general formula of aliphatic ethers is CnH2n+2O, the same as that of monohydric alcohols. Thus, aliphatic ethers and monohydric alcohols are isomers known as functional group isomers. e.g. C2H5-OH and CH3−O−CH3 are the functional group isomers.
Ether Definition
Ethers are a class of organic compounds which contain an oxygen atom bonded to two alkyl/aryl groups (same or different).
Structure of Ethers
In ethers, on oxygen the two bond pairs and two lone pairs are arranged in tetrahedral structure. But the bond angle is slightly greater than the tetrahedral angle due to the repulsion between the two bulky groups which is known as bond pair- bond pair repulsion. The Structural Formula of Ether is shown below:
R-O-R’
Ar-O-Ar
where,
- [R- Alkyl group]
- [Ar- Aryl group]
Examples of Ethers
Examples of Ethers are mentioned below:
- CH3-O-CH3 – Methoxymethane
- CH3-O-C2H5 – Ethoxymethane
- C6H5-O-C6H5 – Diphenyl ether
Diphenyl Ethers
In Diphenyl Ether, phenyl group (C6H5) is attached on both sides of oxygen atom. It is a type of aryl ethers.
Example: C6H5-O-C6H5
Glycol Ethers
In Glycol Ethers both the functional groups i.e. ether and alcohol are present in the same molecule.
Example: CH3CH(OH)CH2-O-CH2CH(OCH3)CH3
Vinyl Ethers
Ethers which have a strongly electron donating alkoxy substituent readily form polymers on treatment with an acidic compound (initiator).
Example: CH2=CH-OR
Cyclic Ethers
Ethers which forms a closed ring are known as cyclic ethers. According to IUPAC System 3 or 4 membered rings are known as Oxiranes and Oxetanes respectively. They are also called epoxyalkanes.
Naming Ethers
Common names of ethers are derived from the names of alkyl/aryl groups written as separate words in alphabetical order and adding the word ether at the end.
Examples of Nomenclature of Ether
The common name of Ethers is done as follows:
- CH3-O-CH3 – Dimethyl Ether
In the above example, the two substituent are Methyl Group, hence, the name is written as Dimethyl Ether.
- C2H5-O-C2H5 – Diethyl Ether
In the above example, the two substituent are ethyl Group, hence, the name is written as Diethyl Ether.
- CH3-O-C2H5 – Ethylmethyl Ether
In the above Example, the two substituent are ethyl and methyl. In dictionary order, ethyl comes first. Hence, the compound is named as Ethylmethyl Ether
IUPAC Naming of Ethers
The IUPAC Nomenclature of Ethers is done using the rules mentioned below:
- Rule 1: Select the longest carbon chain as the parent chain
- Rule 2: Change the name of the other carbon group ends with ‘yl’ into ‘oxy’. For Example, Ethyl becomes ethoxy.
Example of IUPAC Naming of Ether
The IUPAC Nomenclature of Ether is done as follows:
- CH3 –O-CH3 – Methoxymethane
In the above example, methyl is substituent on both sides of oxygen. Hence, one methyl will be named as Methoxy and other will be named as Methane. Hence, the name of the compound is Methoxymethane
- CH3CH2-O-CH2CH3 – Ethoxyethane
In the above example, ethyl is substituent on both sides of oxygen. Hence, one ethyl will be named as ethoxy and other will be named as ethane. Hence, the name of the compound is Ethoxyethane
- CH3-O-C2H5 – Methoxyethane
In the above example, methyl and ethyl are two different substituent. Ethyl having larger carbon atom will be considered as parent chain and added as suffix “Ethane” while methyl having lower carbon will named as Methoxy and added as Prefix. Hence, the compound is named as Methoxymethane
Types of Ethers
Ethers are classified into following types
- Simple or symmetrical ethers
- Mixed or unsymmetrical ethers
- Aliphatic ethers
- Aromatic ethers
- Polyethers
- Crown ethers
- Phenolic ethers
In Ethers oxygen atom is present between two alkyl/aryl groups. If both the groups are same then it is said to be symmetrical or simple ethers and if the groups are different then it is said to be unsymmetrical or mixed ethers.
Simple Ethers (Symmetrical Ethers)
In Simple Ethers, both the alkyl/aryl groups are same on both the sides of oxygen atom. Examples of Simple Ethers include
- CH3-O-CH3 (Dimethyl ether)
- C2H5-O-C2H5 (Diethyl ether)
- C6H5-O-C6H5 (Diphenyl ether)
Mixed Ethers (Usymmetrical Ethers)
Mixed Ethers are the ether in which both the alkyl/aryl groups are different on both the sides of oxygen atom. Examples of Mixed Ethers are shown below:
- CH3-O-C2H5 (Ethyl methyl ether)
- C2H5-O-C3H7 (Ethyl propyl ether)
- C6H5-O-CH3 (Methyl phenyl ether)
Aliphatic Ethers
Aliphatic Ethers are those in which R and R’ whether same or different, both are Alkyl Groups. Example of Aliphatics ethers are
- CH3-O-CH3 (Dimethyl ether)
- C2H5-O-CH3 (Ethyl methyl ether)
- CH3-CH2-CH2-O-CH3 (Methyl propyl ether)
Aromatic Ethers
Ethers in which either one or both R and R’ groups are aryl groups are called Aromatic Ethers. Examples of Aromatic Ethers are mentioned below:
- C6H5-O-CH3 (Methyl phenyl ether)
- C6H5-O-C2H5 (Ethyl phenyl ether)
- C6H5-O-C6H5 (Diphenyl ether)
Polyethers
Polyethers are polymers(large single unit) which are made up of combining monomers (small units) joined together by ether linkages (two carbon atoms bonded to an oxygen atom). A variety of polyethers are produced, ranging from elastomers to engineering plastics. They can be either aliphatic or aromatic polyethers. Examples of Polyethers are
- [-CH2O-]n
- [-CH2CH2O-]n
Crown Ethers
Class of ethers which strongly bind certain cations, forming complexes are known as Crown ethers. The oxygen atoms are well situated and form coordinate bond with a cation located at the interior of the ring, whereas the exterior of the ring is hydrophobic. The resulting cations often form salts that are soluble in nonpolar solvents, and for this reason crown ethers are useful in phase transfer.
Phenolic Ethers
Ethers in which one of the groups is alkyl while the other group is aryl then they are said to be phenolic ethers. They are also known as aryl alkyl ethers. Examples of Phenolic Ethers are mentioned below:
- C6H5-O-CH3 (Methyl phenyl ether)
- C6H5-O-C2H5 (Ethyl phenyl ether)
Isomerism in Ethers
Ethers show following types of isomerism
- Functional Group Isomerism
- Metamerism
- Chain Isomerism
Functional Group Isomerism
Ethers show this type of isomerism with monohydric alcohols as they have same general formula i.e. CnH2n+2O but have different functional group.
Example of Functional group isomerism is,
Molecular formula |
Alcohol |
Ether |
---|---|---|
C2H6O |
CH3CH2OH (ethanol) |
CH3-O-CH3 (dimethyl ether) |
C3H8O |
C3H7OH (propanol) |
CH3-O-C2H5 (ethyl methyl ether) |
Metamerism
Ethers show isomerism among themselves in which they are having same molecular formula but different carbon groups on both sides of oxygen atom.
Molecular formula |
Ether |
Ether |
---|---|---|
C4H10O |
C2H5-O-C2H5 (Diethyl Ether) |
CH3-O-C3H7 (Methyl Propyl Ether) |
Chain Isomerism
Ethers having different carbon chain i.e. branching thus exhibiting different structures but have same molecular formula are called chain isomerism.
Molecular Formula |
Ether |
Ether |
---|---|---|
C5H12O |
CH3CH2CH2CH2-O-CH3 (1-methoxy butane) |
(CH3)2CHCH2-O-CH3 (1-methoxy-2-methyl propane ) |
Physical Properties of Ethers
Sorm of the physical properties of the Ethers are,
- Density: Ethers are lighter than water. Lower ethers are highly volatile and very inflammable.
- Dipole Moment: In ethers the C-O-C bond angle is not 180° due to the repulsion between the lone pairs on oxygen so ethers have a low dipole moment making the ethers somewhat polar.
- Boiling Point: Due to low dipole moment Ethers have low boiling point. Boiling points of ethers increase with increase in molecular mass. The boiling points of ethers are close to the boiling points of alkanes.
- Solubility: Lower ethers are soluble in water. As molecular mass increases, the solubility of ether in water decreases. Solubility of lower ethers in water is due to hydrogen bonding between ether and water molecules. Ethers are soluble in water because the oxygen atom in ethers forms hydrogen bond with water molecules. But solubility decreases as the no. of carbon atom increases.
Chemical Properties of Ethers
Ethers are chemically less reactive as they do not have any active functional group. They do not react with bases, reducing agent, oxidising agent and active metals etc. under ordinary conditions but undergo chemical reactions under specific conditions.
Thus, the properties of ethers are due to the alkyl groups, lone pairs of electrons on oxygen atom and cleavage of C-O bond.
Hydrolysis of Ethers
Hydrolysis of Ether is a reaction where a water molecule acts as one of the reactants and reacts with ether forming alcohols. Simple ethers on hydrolysis gives same type of alcohols whereas mixed ethers on hydrolysis gives different types of alcohols.
The general reaction for hydrolysis of ether is shown below.
R−O−R +H2O→R−OH + R−OH
R-O-R’ +H2O→R-OH + R’-OH
Examples of Hydrolysis of Ether
- C2H5−O−C2H5 + H2O→C2H5OH + C2H5OH
- CH3-O-C2H5 + H2O→CH3OH + C2H5OH
Formation of Peroxide
Due to the presence of lone pair of electrons on the oxygen of Ether , when ether comes into contact with atmospheric oxygen in the presence of sunlight, it reacts with oxygen to form ether peroxide. Ether peroxide is highly unstable and explodes violently when heated, resulting in serious accidents.
Friedel Craft Reaction
In this Anisole undergoes the Friedel-Crafts reaction, which involves introducing alkyl and aryl groups at ortho and para positions via reactions with an alkyl halide and acyl halide of Anisole in the presence of anhydrous aluminium chloride (a Lewis acid) as a catalyst.
Nitration
In this type of reaction, Aromatic ethers in presence of conc. HNO3 or conc. H2SO4 undergoes nitration and NO2 is added on aromatic ethers.
Example- Anisole in presence of conc. H2SO4 undergoes nitration reaction to form 2-Nitroanisole which is a minor product and 4-Nitroanisole which is a major product.
Halogenation
Phenyl Alkyl ethers undergo typical halogenation in the benzene ring.
For example, Anisole undergoes bromination with bromine in ethanoic acid even in the absence of an iron (III) bromide catalyst. It is caused by the methoxy group activating the benzene ring. The para isomer is obtained as a major product.
Synthesis of Ethers
Ethers can be synthesized by following methods
- William Ether Synthesis
- Dehydration of Alcohol
Williamson Ether Synthesis
In Williamson Ether Synthesis reaction alkyl halides react with sodium alkoxide to form ether and sodium halide. This is a nucleophilic substitution reaction(Sn2 reaction).
R-ONa + R’X → R-O-R’ + NaX
Example:
C2H5ONa + C2H5I → C2H5-O-C2H5 + NaI
This reaction is based on the nucleophilic substitution of alkyl halides in which the halogen atom is replaced by alkoxy group by SN2 mechanism.
Dehydration of Alcohols
Dehydration of Alcohols happens when an excess of alcohol is heated at 413K in presence of protic acids (H2SO4) then two molecules of alcohol eliminate one molecule of water to form ether. Lower ethers are prepared on a large scale by this method.
R-OH + R-OH → R-O-R + H2O
Example:
C2H5OH + C2H5OH → C2H5-O-C2H5 + H2O
Esters and Ethers
The major distinguishing factor between ether and ester is that in ether there is two carbon atoms and in between one oxygen atom is present and there is no double bond present between oxygen and carbon atoms whereas in ester two carbon atoms is present with two oxygen atoms between them and one oxygen forming double bond with carbon atom.
- Formula of Ether is R-O-R
- Formula of Ester is R-COOR
The difference between Ester and Ether is tabulated below:
Difference Between Ethers and Esters |
|
---|---|
Ethers |
Esters |
In this an oxygen atom forms single bonds with two carbon atoms separately. |
In this a carbonyl group is bonded to ether functional group. |
General formula- R-O-R’ |
General formula- RCOOR’ |
Their boiling and melting points are less. |
Their melting and boiling points are high. |
They are derived from alcohols. |
They are derived from carboxylic acids. |
They are less reactive than esters. |
They are more reactive than ethers. |
They are non polar in nature. |
They are polar in nature. |
They have only sigma bonds. |
They have sigma and pi bonds. |
Example- CH3-O-CH3 (dimethyl ether) |
Example- CH3COOCH3 (methyl acetate) |
Uses of Ethers
The uses of Ethers are mentioned below:
- Ethers are good solvents for the extraction of many organic compounds as they are chemically inert.
- Diethyl ether is used as a refrigerant.
- They are used as dewaxing for lubricating oils.
- The mixture of alcohol and ether is used as a substitute of petrol.
- It is also used in the production of smokeless powders.
- It is used as an inhalation anaesthetic agent in surgery because it produces unconsciousness without affecting lung and heart.
Also, Check
Ether IIT JEE Questions
Q1. An ether is more volatile than an alcohol having the same molecular formula. What is the reason for this difference?
- Dipolar character of ethers
- Alcohols having resonance structures
- Inter-molecular hydrogen bonding in ethers
- Inter-molecular hydrogen bonding in alcohols
Q2. Ethers may be used as solvents because they react only with which of the following reactants?
- Acids
- Bases
- Oxidising agent
- Reducing agents
Q3. What are the products when tert-butyl ethyl ether is cleaved with concentrated HI?
- Iodoethane and tert-butanol
- Iodoethane and 2-iodo-2-methylpropane
- Ethanol and 2-iodo-2-methylpropane
- Ethanol and tert-butanol
Q4. Which pair of products would result from the acid cleavage of phenyl propyl ether with excess concentrated HBr at an elevated temperature?
- Phenol and 1-propanol
- Bromobenzene and 1-propanol
- Bromobenzene and 1-bromopropane
- Phenol and 1-bromopropane
Ether – FAQs
1. What are Phenyl Ethers?
Pehenyl Ether are type of aryl ethers having phenyl group (-C6H5) attached with O.
2. What are Enol Ethers?
They are the ethers having alkene(double bond) with an alkoxy substituent. The general structure is R2C=CR-OR where R = H, alkyl or aryl.
3. What is the Chemical Formula of Ether?
The chemical formula of Ether is R-O-R where R is Alkyl or Aryl group
4. What is an Example of Ether?
An example of Ether is Dimethyl Ether which is written as CH3-O-CH3
5. What is the Molecular Formula of Ester and Ether?
Ester is derived from carboxylic acid and has the molecular formulae RCOOR whereas Ether is derived from alcohol and has the molecular formulae R-O-R.
6. What is the Use of Ether?
Various uses of Ethers are,
- Antiseptic Agent
- Anasthetic Agent, etc.
Contact Us