Structural Isomerism

Structural isomerism

Isomerism is the phenomenon in which two or more compounds have the same molecular formula but different structures, and therefore, different properties. One of the types of isomerism is structural isomerism, which is further classified into different subtypes.

 

Chain isomerism

 

Chain isomerism is a subtype of structural isomerism in which two or more compounds have the same molecular formula but different carbon skeletons. In other words, their carbon atoms are arranged in different ways.

 For example, C5H12 represents three different compounds that are chain isomers: n-pentane, 2-methylbutane, and 2,2-dimethylpropane.

In n-pentane, the five carbon atoms are arranged in a straight chain, while in 2-methylbutane, the carbon chain is branched at the second carbon atom. In 2,2-dimethylpropane, the carbon chain is highly branched and the molecule is symmetrical.

 Chain isomerism is important in organic chemistry because it can affect the physical and chemical properties of a compound, such as its boiling point, melting point, and reactivity.

 

 

Position isomerism

Position isomerism is a type of structural isomerism where two or more compounds have the same molecular formula but differ in the position of a functional group or substituent atom on the carbon skeleton.

In the given example, the molecular formula C3H8O represents two alcohols, which are position isomers.

The two alcohols that can be formed with the given molecular formula C3H8O are propan-1-ol and propan-2-ol. Propan-1-ol has the hydroxyl (-OH) group attached to the first carbon atom, whereas propan-2-ol has the hydroxyl group attached to the second carbon atom.

 Thus, in position isomerism, the molecular formula remains the same, but the position of the functional group or substituent atom on the carbon skeleton changes, leading to the formation of different isomers with distinct chemical and physical properties.

 

 

Functional group isomerism

Functional isomerism is a type of isomerism where two or more compounds have the same molecular formula but different functional groups. In the given example, the molecular formula C3H6O represents two compounds with different functional groups - an aldehyde and a ketone.

 

In an aldehyde, the functional group is a carbonyl group (-CHO) which is located at the end of a carbon chain. In the given example, propanal is an aldehyde with the molecular formula C3H6O. On the other hand, in a ketone, the carbonyl group (-C=O) is located in the middle of a carbon chain. The other compound represented by the molecular formula C3H6O is propanone, which is a ketone.

 

 

Metamerism

 

It arises due to different alkyl chains on either side of the functional group in the molecule. For example, C4H10O represents methoxy propane (CH3OC3H7) and ethoxyethane (C2H5OC2H5).