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Isomerism - Coggle Diagram
Isomerism
Structural Isomerism
: Compounds with the same molecular formula but different atomic arrangement
Positional
: The same functional group but different positions ( 1,2-dibromobenzene, 1,3-dibromobenzene and 1,4-dibromobenzene)
Chain
: Different arrangement of carbon chain of molecules – Butane and 2-methyl propane
Functional Group
: different functional groups (C2H6O can be an alcohol or an ether)
Stereoisomerism
- Molecules with atoms attached in the same order but with different spatial arrangements
Configurational
- Can be interconverted by breaking the bonds
Cis/trans and E/Z isomers
- restricted rotation around atoms
Alkenes
Cyclic compounds
Has to have different atoms or groups of atoms bonded on the sides
Cis - isomer with same groups on the same side
Trans - isomer that has the same groups on opposite sides
Optical Isomerism
- Chirally exist when there is an asymmetric carbon atom
Chiral
- a carbon that is attached to 4 different groups/atoms
Enantiomers-
Chiral molecules have no plane of symmetry, the optical isomers are non-superimposable and are mirror images of one another
1)
Optical
Activity
- Optical isomers show a difference in specific interaction with light
Ordinary light has electromagnetic waves that oscillate in an infinite range of planes
Light is passed through a polariser, the light waves only oscillate in a single plane- plane-polarised light
When a beam of plane polarised light is passed through a solution of optical isomers, they rotate
The amount and direction of rotation is measured by a polar-meter
Two enantiomers rotate the plane-polarised light in equal and opposite directions, a racemic mixture does not rotate the light so it is optically inactive
2) Reactivity with Other Chiral Molecules
Racemic mixture reacted with another chiral compound would lead to two different products (for both enantiomers)
Products have distinct physical and chemical properties - resolution separates
Diastereomers-
Opposite configurations at one or more but not all chiral centres (not mirror images)
Conformational
- Can be interconverted by rotation