Priority order of Structural Isomers: Types and defination

Today we are going to discuss about structural isomers. It's types and definations.

Q. What is Structural Isomerism?

Ans: Structural Isomerism is shown by the compounds having the same molecular formula but different structural formulae differing in the arrangement of the atoms.

There are several types of structural isomerism, and they can be categorized based on the nature of the isomeric relationship. Here are some common types of structural isomerism, along with examples:

1. Chain Isomerism:

Isomers differ in the arrangement of carbon atoms in the carbon skeleton.

e.g. Butane (straight-chain) and Isobutane (branched-chain) are chain isomers.

2. Position Isomerism:

Isomers differ in the position of functional groups or substituents on the carbon skeleton.

e.g.  1-Butanol and 2-Butanol are position isomers; they have the same molecular formula (C4H10O) but different positions of the -OH group on the carbon chain.

3. Functional Group Isomerism:

The isomers differ with respect to the nature of functional groups and hence belong to different families.

e.g.  Butanal (an aldehyde) and Butanone (a ketone) are functional group isomers; they both have the molecular formula C4H8O but different functional groups.

4. Tautomeric Isomerism:

Tautomers are actually the functional isomers which exist simultaneously and also in dynamic equilibrium. The isomerism is known as tautomerism.

e.g.  Keto-enol tautomers, where a carbonyl group (-C=O) and a hydroxyl group (-C-OH) rapidly interconvert.

5. Ring-chain Isomerism:

In addition to the various structural isomers listed above, the ring chain isomerism is another type of structural isomerism. As the name suggets, it is present in the open chain and cyclic compounds which are isomeric.

e.g.  Cyclohexane (cyclic) and Hexane (open-chain) are ring-chain isomers.

6. Metamerism:

The metamers differ with respect to the nature of the alkyl groups around a particular functional group. Thus, they belong to the same family.

e.g. The molecular formula C4H10O accounts for three isomeric ethers which are metamers.

The priority order of these structural isomers depends on the context and the specific properties being considered (such as boiling points, reactivity, etc.). Each type of isomerism represents a different way in which atoms can be arranged to form distinct compounds with the same molecular formula. However, if any molecule show two or above structural isomerism the priority order should be --

Ring chain > Tautomers > Functional > Metamers > Chain > Position

This means if a molecule shows chain and position isomerism at the same time, the priority should goes to chain.

Conclusion:

That's all for today. If have any questions don't hesitate to ask a question.