H.
L3 EXTENDED DIPLOMA IN APPLIED SCIENCE
Unit 14: Applications of Organic Chemistry
Assignment 14C: Understand the types, structures,
reactions, uses and properties of isomers
Isomerism
Figure 1- Diagram showing the branches of isomerism (2)
Isomerism refers to the
existence of molecules that
have the same molecular
formula but have different
chemical and physical
properties, also known as
isomers (1). There are different
forms of isomerism: structural
and stereoisomerism. Within
these different forms of
isomerism, there are different
types of isomers that arise- see Figure 1.
Structural isomerism
Structural isomerism is defined as compounds with the same molecular formula
but different structural formula, for example propene and cyclopropane- see
Figure 2. As seen in Figure 2, the two molecules have the same molecular
formula but differ in structure. This can be seen more clearly in 3D models-
shown in Figure 3.
Figure 2- Structural isomers, propene, and Figure 3- 3D models of structural isomers, propene
cyclopropane (3) on the left and cyclopropane on the right (3)
Furthermore, there are different types of structural isomerism: chain, positional
and functional group isomerism (3).
Chain isomerism occurs when compounds have the same molecular formula, but
their longest hydrocarbon chain is different (3). An example of chain isomerism is
pentane and 2,2-dimethyl propane- see Figure 4. As seen in Figure 4, both
molecules have the same molecular formula, C5H12, with a different arrangement
of the carbon chain- pentane’s carbon chain is straight and 2,2-dimethyl propane
is branched. 3D models of this example are shown in Figure 5.
Figure 5- 3D models of chain
Figure 4- Chain isomers, pentane, and 2,2-dimethyl propane (3) isomers, pentane (top), and 2,2-
dimethyl propane (bottom) (5)
, H.
L3 EXTENDED DIPLOMA IN APPLIED SCIENCE
Unit 14: Applications of Organic Chemistry
A different example of chain isomerism is butane and methylpropane- see Figure
6. These molecules have the same molecular formula of C 4H10 with a different
structural arrangement of the carbon chain. As seen in Figure 6, methylpropane
has a branched chain and butane has a straight chain.
Figure 6- Chain isomers, butane, and methylpropane (6)
Positional isomerism, however, has the same longest hydrocarbon chain with the
same atoms/groups of atoms attached (6). The only difference for this type of
structural isomerism is that the atom/group of atoms is attached to a different
carbon atom- see Figure 7 for an example (6). As seen in Figure 7, both
molecules have the same atoms attached with the chlorine attached to the first
carbon in 1-chlorobutane and the second carbon in 2-chlorobutane.
Figure 7- Positional isomers, 1-chlorobutane, and 2-chlorobutane (6)
Another example of positional isomerism is butanol and 2-butanol- these
molecules have an OH group attached to different carbons. As seen in Figure 8,
the first carbon has the OH group attached in butanol and the second carbon has
the OH group attached in 2-butanol. This can be seen more clearly in Figure 9.
Figure 9- 3D models of positional isomers,
Figure 8- Positional isomers, butanol, and 2-butanol (3) butanol (top), and 2-butanol (bottom) (7)
L3 EXTENDED DIPLOMA IN APPLIED SCIENCE
Unit 14: Applications of Organic Chemistry
Assignment 14C: Understand the types, structures,
reactions, uses and properties of isomers
Isomerism
Figure 1- Diagram showing the branches of isomerism (2)
Isomerism refers to the
existence of molecules that
have the same molecular
formula but have different
chemical and physical
properties, also known as
isomers (1). There are different
forms of isomerism: structural
and stereoisomerism. Within
these different forms of
isomerism, there are different
types of isomers that arise- see Figure 1.
Structural isomerism
Structural isomerism is defined as compounds with the same molecular formula
but different structural formula, for example propene and cyclopropane- see
Figure 2. As seen in Figure 2, the two molecules have the same molecular
formula but differ in structure. This can be seen more clearly in 3D models-
shown in Figure 3.
Figure 2- Structural isomers, propene, and Figure 3- 3D models of structural isomers, propene
cyclopropane (3) on the left and cyclopropane on the right (3)
Furthermore, there are different types of structural isomerism: chain, positional
and functional group isomerism (3).
Chain isomerism occurs when compounds have the same molecular formula, but
their longest hydrocarbon chain is different (3). An example of chain isomerism is
pentane and 2,2-dimethyl propane- see Figure 4. As seen in Figure 4, both
molecules have the same molecular formula, C5H12, with a different arrangement
of the carbon chain- pentane’s carbon chain is straight and 2,2-dimethyl propane
is branched. 3D models of this example are shown in Figure 5.
Figure 5- 3D models of chain
Figure 4- Chain isomers, pentane, and 2,2-dimethyl propane (3) isomers, pentane (top), and 2,2-
dimethyl propane (bottom) (5)
, H.
L3 EXTENDED DIPLOMA IN APPLIED SCIENCE
Unit 14: Applications of Organic Chemistry
A different example of chain isomerism is butane and methylpropane- see Figure
6. These molecules have the same molecular formula of C 4H10 with a different
structural arrangement of the carbon chain. As seen in Figure 6, methylpropane
has a branched chain and butane has a straight chain.
Figure 6- Chain isomers, butane, and methylpropane (6)
Positional isomerism, however, has the same longest hydrocarbon chain with the
same atoms/groups of atoms attached (6). The only difference for this type of
structural isomerism is that the atom/group of atoms is attached to a different
carbon atom- see Figure 7 for an example (6). As seen in Figure 7, both
molecules have the same atoms attached with the chlorine attached to the first
carbon in 1-chlorobutane and the second carbon in 2-chlorobutane.
Figure 7- Positional isomers, 1-chlorobutane, and 2-chlorobutane (6)
Another example of positional isomerism is butanol and 2-butanol- these
molecules have an OH group attached to different carbons. As seen in Figure 8,
the first carbon has the OH group attached in butanol and the second carbon has
the OH group attached in 2-butanol. This can be seen more clearly in Figure 9.
Figure 9- 3D models of positional isomers,
Figure 8- Positional isomers, butanol, and 2-butanol (3) butanol (top), and 2-butanol (bottom) (7)
