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stereoisomers
Isomers having the same molecular structure, but differing in the spatial arrangement of their atoms. There are two main types.
Optical isomers are asymmetric molecules – usually having an asymmetric carbon atom with four different groups bonded to it – which hence have two mirror-image forms (enantiomers) and show optical activity. Absolute spatial configurations have now been found for many isomers, and may be represented by projection formulae. Resolution, i.e., separation of the two enantiomers, is achieved by combining them with a single optical isomer, thus producing a pair of diastereoisomers which, not being mirror-images, have different properties and are separable. Inversion of configuration often occurs in substitution reactions.
Geometrical isomers contain groups which are differently oriented with respect to a double bond or ring where rotation is impossible; they have different properties.
Related category
• ORGANIC CHEMISTRY
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