ISOMERS
They are molecules that have the same molecular formula, but a different arrangement of atoms in space.
STEREOISOMERS STRUCTURAL ISOMERS
The molecules have the same molecular formula The atoms are arranged in a completely different order.
and the same structural formula, but the spatial Positional isomerism is when the atom arrangement is different
however there is no change to the functional group. Functional
arrangement of the atoms is different. isomerism is when the atom arrangement differs and causes a
change in the functional group between the two isomers.
CONFIGURATIONAL ISOMERS CONFORMATIONAL ISOMERS
Interconversion of configurational isomers requires the Conformational isomers are forms of the same molecule, which have
breaking and re-forming of covalent chemical bonds. different conformations due to rotation about a sigma bond. The
conformation of the molecule refers to the spatial orientation of a
portion of the molecule relative to another. It is not directly related to
the covalent bonds but with their rotation. Doesn’t have to involve all
the single bonds and doesn’t require bonds to be broken or created
during interconversion.
OPTICAL ISOMERS CIS-TRANS ISOMERS + E/Z ISOMERS
Isomers with the same molecular and structural formula but different Occurs in alkenes and cyclic compounds as this prevents bond rotation. The two
spatial arrangement of atoms. They are non-superimposable (mirror compounds have the same structural formula, but the groups are arranged
images). In order to exhibit this, there must be four different groups differently in space around the double bond or ring. Cis isomers occur when the
groups/atoms are on the same side of the double bond, and trans isomers occur
attached to a carbon atom; this is called a chiral centre. For ring
when they are on opposite sides. For a molecule to exhibit cis-trans isomerism
compounds, if the molecule has a plane of symmetry it will not there must be two different groups on both sides of the double bond. Molecules
exhibit optical isomerism. Optical isomers have the ability to rotate with higher priority groups (based on atomic number) on the same side of the
the plane of polarisation of plane-polarised in opposite directions. double bond are Z isomers, and molecules with higher priority groups on
They have identical physical properties (apart from effect on plane- opposite sides are E isomers. They may have different chemical properties.
polarised light), and identical chemical properties with compounds
that aren’t optically active.
They are molecules that have the same molecular formula, but a different arrangement of atoms in space.
STEREOISOMERS STRUCTURAL ISOMERS
The molecules have the same molecular formula The atoms are arranged in a completely different order.
and the same structural formula, but the spatial Positional isomerism is when the atom arrangement is different
however there is no change to the functional group. Functional
arrangement of the atoms is different. isomerism is when the atom arrangement differs and causes a
change in the functional group between the two isomers.
CONFIGURATIONAL ISOMERS CONFORMATIONAL ISOMERS
Interconversion of configurational isomers requires the Conformational isomers are forms of the same molecule, which have
breaking and re-forming of covalent chemical bonds. different conformations due to rotation about a sigma bond. The
conformation of the molecule refers to the spatial orientation of a
portion of the molecule relative to another. It is not directly related to
the covalent bonds but with their rotation. Doesn’t have to involve all
the single bonds and doesn’t require bonds to be broken or created
during interconversion.
OPTICAL ISOMERS CIS-TRANS ISOMERS + E/Z ISOMERS
Isomers with the same molecular and structural formula but different Occurs in alkenes and cyclic compounds as this prevents bond rotation. The two
spatial arrangement of atoms. They are non-superimposable (mirror compounds have the same structural formula, but the groups are arranged
images). In order to exhibit this, there must be four different groups differently in space around the double bond or ring. Cis isomers occur when the
groups/atoms are on the same side of the double bond, and trans isomers occur
attached to a carbon atom; this is called a chiral centre. For ring
when they are on opposite sides. For a molecule to exhibit cis-trans isomerism
compounds, if the molecule has a plane of symmetry it will not there must be two different groups on both sides of the double bond. Molecules
exhibit optical isomerism. Optical isomers have the ability to rotate with higher priority groups (based on atomic number) on the same side of the
the plane of polarisation of plane-polarised in opposite directions. double bond are Z isomers, and molecules with higher priority groups on
They have identical physical properties (apart from effect on plane- opposite sides are E isomers. They may have different chemical properties.
polarised light), and identical chemical properties with compounds
that aren’t optically active.
