Alcohols And Ethers, Isomerism, Important Topics For JEE 2024

Alcohols And Ethers : Isomerism is the phenomenon where multiple compounds with distinct chemical structures, but the same chemical formula coexists. When substances have the same molecular formula but distinct functional groups, this is known as functional group isomerism. Isomers of the functional group are members of distinct homologous series. In this article we will study alcohol and ethers isomerism.

Isomerism in alcohol

Isomerism in alcohol  : Alcohol exhibits three different forms of structural isomerism. Consequently, chain isomerism, position isomerism and functional group isomerism.

Chain Isomerism: Chain isomerism occurs in alcohols with at least four carbon atoms because the longest chains' C-skeletons have a different structure.

Position isomerism: Position isomerism occurs in alcohols with at least three carbon atoms because the hydroxy group (OH) is positioned differently in these molecules.

Isomerism in ether: Aliphatic Ethers can give two different types of isomers.

Metamerism: Metamerism is frequently found in ethers. The nature of alkyl groups can vary in this isomerism. This is due to the unequal distribution of carbon atoms on both sides of the functional groups.

CH ₃ CH ₂ –O–CH ₂ CH ₃ (Diethyl ether) CH ₃ –O–CH ₂ CH ₂ CH ₃ (Methyl propyl ether)

Functional group Isomerism

Functional group Isomerism: There are three pairs of these isomers you need to be aware of:

• Alcohols and ethers
• Aldehydes and ketones
• Carboxylic acids and esters

Alcohol and ether isomerism

Alcohol and ether isomerism: Functional isomers are produced by alcohols with two carbon atoms or more. Ether is alcohol’s functional isomer.

CH ₃ –CH ₂ –OH (Ethanol) CH ₃ –O–CH ₃ (Methoxy methane)

Ethanol CH ₃ CH ₂ OH MethoxymethaneCH ₃ OCH ₃

3D model of ethanol                                  3D model of dimethyl ether

The hydroxyl group, —OH, is the functional group found in alcohols. R ₁ –O–R ₂ is the functional group of ethers. The remaining molecule's structures are represented by the symbols R ₁ and R ₂ . If one of them is a hydrogen atom, the compound has a hydroxyl group and is not an ether; otherwise, they can be the same or different. R ₁ and R ₂ in dimethyl ether are methyl groups; they are —CH ₃ groups.

Examples: How Many isomers are possible for formula C ₄ H ₁₀ O, draw their structures?

C ₄ H ₁₀ O