Definition of Isomer
Isomers are molecules with the same molecular formula but different structures. They are classified into structural isomers and stereoisomers.
Structural Isomers
Structural isomers differ in the arrangement of atoms and are further classified into chain, position, and functional isomers.
Stereoisomers
Stereoisomers have identical bonds but differ in the spatial arrangement of groups. They are classified into cis-trans (geometric) isomers, enantiomers, and diastereomers.
Chiral or Asymmetric Center
A chiral or asymmetric center is an atom bonded to four different substituents. A molecule with a chiral center has a non-superimposable mirror image called an enantiomer.
Optical Activity
Enantiomers have almost identical physical properties except for optical activity. One enantiomer rotates polarized light to the right (dextrorotatory), while the other rotates it to the left (levorotatory).
Stereochemistry in Reactions
Radical halogenation reactions on molecules that can form chiral centers produce mixtures of enantiomers in equal amounts or diastereomers in different proportions.
Separation of Enantiomers
Enantiomers have almost identical physical properties, differing in the rotation of polarized light, but having the same melting and boiling points and solubility. Therefore, traditional separation methods cannot be applied, and special techniques are needed. Separation via diastereomers involves transforming the enantiomer mixture into a diastereomer mixture by adding a chiral reagent; diastereomers are easily separable by physical methods.
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