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.

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 C_nH_2n+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.

Crown Ether

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.

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?

1. Dipolar character of ethers
2. Alcohols having resonance structures
3. Inter-molecular hydrogen bonding in ethers
4. Inter-molecular hydrogen bonding in alcohols

Q2. Ethers may be used as solvents because they react only with which of the following reactants?

1. Acids
2. Bases
3. Oxidising agent
4. Reducing agents

Q3. What are the products when tert-butyl ethyl ether is cleaved with concentrated HI?

1. Iodoethane and tert-butanol
2. Iodoethane and 2-iodo-2-methylpropane
3. Ethanol and 2-iodo-2-methylpropane
4. 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?

1. Phenol and 1-propanol
2. Bromobenzene and 1-propanol
3. Bromobenzene and 1-bromopropane
4. 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.