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Chapter 7: Stereochemistry

Summary | Isomer types | Enantiomers | The Stereogenic center | Optical Activity | Absolute Relative Configuration | Cahn-Ingold-Prelog R/S notation | Fischer projections | Self Assessment | Quiz |

Isomer types

Chapter 7 : Stereochemistry

Compounds that have the same molecular formula but different chemical structures are called isomers.
Depending on what types of differences there are between the structures, it is possible to classify isomers into various sub-types.
If you "click" on the named boxes there is a link to a definition and an example.

Types of Isomer tree

Constitutional (or structural) isomers differ in the order in which the atoms are connected so they contain different functional groups and / or bonding patterns:

Stereoisomers contain the same functional groups and differ only in the arrangement of atoms in space.

Conformational isomers (or conformers or rotamers) are stereoisomers produced by rotation about sigma bonds, typically rapidly interconverting at room temperature:

Configurational isomers are stereoisomers that do not readily interconvert at room temperature and can (in principle at least) be separated.

Geometric isomers are configurational isomers that differ in the spatial position around a bond with restricted rotation (e.g. a double bond):

Optical isomers are configurational isomers that differ in the 3D relationship of the substituents about one or more atoms:

Enantiomers are optical isomers that are non-superimposable mirror images.

Diastereomers are optical isomers that are not enantiomers.

Deriving Possible Isomers

There is no simple way to know how many isomers exist for a given molecular formula, and therefore, it is important to have a systematic method to derive them. Important preliminary steps in the process are to determine the IHD to see what types of structures you should be considering, then list the functional groups that are possible based on the molecular formula and IHD. Once you have done that, here are a few suggestions to aid the drawing process.....



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