Walden inversion

A Walden inversion or Walden inversion is known within an ongoing chemical reaction, the change in the configuration of a stereochemical center, usually a carbon - atom. Part of this reaction step was named after the Latvian- German chemist Paul Walden, who published his discovery in 1896.

Course of the reaction

During happen SN2 reaction steps in concert: the entry group approaches the central atom, the leaving group is removed through the central atom and the three not directly involved in the reaction substituents on the central atom a planar transition state. Looking at the inlet and outlet group, there is a trigonal bipyramidal transition state where the nucleophile and leaving group are in the apical positions. Similar to the folding of an umbrella, the resulting stereochemical arrangement of the substituents of the reaction product is different from that of the starting material.

If the change of the substituent arrangement is also accompanied by a change in the stereochemical configuration is dependent on the priority of the four residues according to the Cahn -Ingold -Prelog system. To (S) - Corporate entry and leaving group a the same priority in the ranking, so the stereochemical descriptor, for example, of (R ) changes -.