Structural isomerism is a form of isomerism in which molecules with the same molecular formula have atoms bonded together in different orders (as opposed to stereoisomerism.)

Table of contents
1 Chain isomerism
2 Position isomerism
3 Functional group isomerism

Chain isomerism

Chain isomers have components of the chain distinctly ordered to create different structures. Here, 3-methylpentane has become 2-methylpentane:

Position isomerism

Positional isomers occur when a functional group changes position on the chain. In the diagram, 2-hydroxypentane has become 3-hydroxypentane:

Functional group isomerism

Functional group isomerism is when a functional group splits up and becomes a different group. Here, butan-1-ol has become ethoxyethane: