Question

Explain various types of constitutional isomerism (structural isomerism) in organic compounds.

Answer 1

Constitutional isomers:

These isomers having the same molecular formula but differ in their bonding sequence. 

It is classified into 6 types:

1. Chain (or) nuclear (or) skeletal isomerism: The phenomenon in which the isomers have similar molecular formula but differ in the nature of carbon skeleton (i.e., straight (or) branched)

e.g., C₅H₁₂

1.

2. 

3. 

2. Position isomerism:

If different compounds belonging to same homologous series with the same molecular formula and carbon skeleton but differ in the position of substituent or functional group or an unsaturated linkage are said to exhibit position isomerism.

e.g., C₅H₁₀ :

1.

2.

3. Functional isomerism:

Different compounds having same molecular formula but different functional groups are said to exhibit functional isomerism.

e.g., C₃H₆O:

(i) CH₃-CH₂-CH₂-CH=CH₂ propanal (Aldehyde group)

(ii) 

4. Metamerism:

This isomerism anses due to the unequal distribution of carbon atoms on either side of the functional group or different alkyl groups attached to either side of the same functional group and having same molecular formula.

e.g., C₄H₁₀O:

1. 

2. 

3. 

5. Tautomerism:

It is an isomerism in which a single compound exists in two readily inter convertible structures that differ markedly in the relative position of atleast one atomic nucleus generally hydrogen.

e.g., C₂H₄O:

6. Ring chain isomerism:

It is an isomerism in which compounds having same molecular formula but differ in terms of bonding of carbon atom to form open chain and cyclic structures.

e.g., C₂H₆:

1.

2.