Stereoselektivitäten

Stereoselektivität refers to the preference of a chemical reaction to form one stereoisomer over other possible stereoisomers. Stereoisomers are molecules that have the same molecular formula and connectivity but differ in the spatial arrangement of their atoms. In many chemical reactions, especially those involving chiral centers or the formation of new chiral centers, multiple stereoisomers can theoretically be produced. Stereoselective reactions, however, will predominantly yield a single stereoisomer, or an enriched mixture of a particular stereoisomer.

This preference arises from the difference in energy between the transition states leading to the various stereoisomeric products. The transition state with the lowest energy will be favored, leading to the formation of the corresponding stereoisomer as the major product. Factors influencing stereoselectivity include steric hindrance, electronic effects, and the presence of chiral auxiliaries or catalysts.

Stereoselectivity is a crucial concept in organic chemistry and has significant implications in fields such as pharmaceutical synthesis, where the biological activity of a drug often depends critically on its specific stereochemistry. For example, one enantiomer of a drug might be therapeutically effective, while the other could be inactive or even toxic. Therefore, controlling stereoselectivity in synthetic pathways is paramount for producing pure and effective chiral compounds. Different types of stereoselective reactions exist, including diastereoselective and enantioselective reactions, each describing a specific type of stereoisomeric preference.