BTEC applied science: unit 14 Learning aim C: Understand types, structures, reactions, uses and properties of isomers.

Learning aim C: Understand types, structures, reactions, uses and
properties of isomers.

P4: Explain the different types of structural isomerism and stereoisomerism




Structural Isomerism

Structural isomers are compounds that have the same molecular formula but different structural
formula.

There are 3 different types of structural isomerism:

● Chain isomerism
● Positional isomerism
● Functional group isomerism

Chain isomers

, butane, also known as unbranched butane, and isobutane, commonly known as i-butane. These
isomers are known as butane and 2-methylpropane in IUPAC nomenclature


Because isomers are separate molecules, their properties differ. Branched-chain isomers
typically have lower boiling and melting points than straight-chain isomers. Iso-butane, for
example, has boiling and melting temperatures of -12 °C and -160 °C, respectively, whereas
n-butane has 0 °C and -138 °C. The lower the boiling and melting points, the more branching
there is. Natural gas liquids and refinery gas streams can be used to produce isomers of butane


Positional isomers arise from differences in the position of a functional group in each isomer.
The functional group can be located on different carbons