Unit 14: applications of organic chemistry
Learning aim C: understand types, structure, reactions, use and properties of
isomers.
Assignment title: designing molecules
P4:
Isomerism
A compound that has the same chemical formula, but a distinct atom arrangement is called an isomer.
Stereoisomerism and structural isomerism are the two different types of isomerism. Compounds can
have a variety of characteristics and reactions as a result of different isomers. Nevertheless, the
molecular structure will not change. Chain, position, and functional structural isomerism are the three
categories. The two categories of stereoisomerism are optical and geometrical.
What is structural isomerism?
Structural isomerism is any molecule that has the same molecular formula but different structural
formulae. There are different types of structural isomerism such as chain, positional and functional
group isomerism.
Chain
When a molecule's formula is the same, but its carbon chain can either be straight or branched, the
substance is said to be a structural chain isomer. The molecule's IUPAC name also changes to reflect this
new rearrangement. As shown in the two instances below, both molecules have the same chemical
formula, but the first example has a straight carbon chain, whilst the second example has a branched
chain.
Example 1 Example 2
Butane (C4H10) Methylpropane
(C4H10)
Structural Structural formulae:
formulae
3d model 3d model:
, Positional
Positional isomerism is about the position, the function group of the molecule can be in different place
on the carbon chain. This can reflect on the IUPAC name of the molecule, when the functional group
changes its place so does the name. But the molecular formula remains the same. The examples below,
the (OH) atom is in a different position. As you can see the molecular formula of the compound has not
changed, however, the name has changed. These changes in the position can bring different properties
and reactions to the compounds.
Example 1 Example 2
Propan-1-ol (C3H7OH) propan-2-ol (C3H7OH)
Structural formulae: Structural formulae:
3d model: 3d model:
Functional
Again, the functional group isomerism about different functional groups. When compounds have the
same molecular formula but contain different functional groups, it is known as functional groups
isomerism. Again, these changes can reflect on the IUPAC name of the compounds. Looking at the
examples below, we can say that the names are different and the functional group, but the molecular
formula is the same.
Example 1 Example 2
Propanal (C3H6O) propanone (C3H6O)
Structural formulae: Structural formulae:
Learning aim C: understand types, structure, reactions, use and properties of
isomers.
Assignment title: designing molecules
P4:
Isomerism
A compound that has the same chemical formula, but a distinct atom arrangement is called an isomer.
Stereoisomerism and structural isomerism are the two different types of isomerism. Compounds can
have a variety of characteristics and reactions as a result of different isomers. Nevertheless, the
molecular structure will not change. Chain, position, and functional structural isomerism are the three
categories. The two categories of stereoisomerism are optical and geometrical.
What is structural isomerism?
Structural isomerism is any molecule that has the same molecular formula but different structural
formulae. There are different types of structural isomerism such as chain, positional and functional
group isomerism.
Chain
When a molecule's formula is the same, but its carbon chain can either be straight or branched, the
substance is said to be a structural chain isomer. The molecule's IUPAC name also changes to reflect this
new rearrangement. As shown in the two instances below, both molecules have the same chemical
formula, but the first example has a straight carbon chain, whilst the second example has a branched
chain.
Example 1 Example 2
Butane (C4H10) Methylpropane
(C4H10)
Structural Structural formulae:
formulae
3d model 3d model:
, Positional
Positional isomerism is about the position, the function group of the molecule can be in different place
on the carbon chain. This can reflect on the IUPAC name of the molecule, when the functional group
changes its place so does the name. But the molecular formula remains the same. The examples below,
the (OH) atom is in a different position. As you can see the molecular formula of the compound has not
changed, however, the name has changed. These changes in the position can bring different properties
and reactions to the compounds.
Example 1 Example 2
Propan-1-ol (C3H7OH) propan-2-ol (C3H7OH)
Structural formulae: Structural formulae:
3d model: 3d model:
Functional
Again, the functional group isomerism about different functional groups. When compounds have the
same molecular formula but contain different functional groups, it is known as functional groups
isomerism. Again, these changes can reflect on the IUPAC name of the compounds. Looking at the
examples below, we can say that the names are different and the functional group, but the molecular
formula is the same.
Example 1 Example 2
Propanal (C3H6O) propanone (C3H6O)
Structural formulae: Structural formulae:
