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Isomerism, Naming - Coggle Diagram
Isomerism
Polarimeter
Principle
Enantiomers are optically active—they rotate through a plane of plane-polarised light. Molecules that cannot do this are optically inactive.
Enantiomers have the same physical properties except their interaction with plane polarised light—this interaction is used to distinguish between two enantiomers.
Plane-polarised light passed through solutions of individual enantiomers --> enantiomers rotate the plane in equal but opposite directions --> rotation of the plane of plane-polarised light is measured by the polarimeter.
Parts
Light source, two polarising filters (one fixed, one can be rotated), and a tube with the enantiomer solution
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Operation
- Unpolarised light is passed through a polarising filter --> plane-polarised light produced
- The plane-polarised light passes through a solution of the enantiomer.
- An analyser is used to determine the angle of rotation of the plane of the plane-polarised light.
Types of mixtures
Solution A: Only enantiomer A, anticlockwise rotation, equal amounts
Solution B: Only enantiomer B, clockwise rotation, equal amounts
Solution C: Both enantiomer A and B in equal amounts, opposite rotations cancel each other out --> racemic or optically inactive mixture
Case study
Thalidomide: Administered as racemic mixture, one enantiomer was effective, the other enantiomer resulted in birth defects
Structural Isomerism
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Functional
When compounds have the same molecular formula, but have different functional groups. Example : Ethanol and dimethyl ether
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Stereoisomerism: molecules that have the same structural formula but differ in the spatial arrangement of atoms
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