Walden Inversion Reaction: Mechanism, Example

A bimolecular nucleophilic substitution (SN₂) reaction results in a change in the configuration of a chiral center known as a “Walden inversion reaction.” This inversion, also known as optical inversion, may or may not result in a change in the direction of rotation. Walden inversion was named after a German chemist, Paul Walden, who discovered it in 1895.

What is Walden Inversion Reaction?

The Walden inversion refers to the inversion of configuration at a chiral center during a bimolecular nucleophilic substitution (SN₂ reaction). Walden inversion changes the structure of the molecule from one enantiomeric form to another because the molecule can produce two enantiomers around the chiral center.

Walden demonstrated in 1986 that (-)-malic acid could be transformed to (+)-malic acid by a series of chemical processes using achiral reagents. This proved that optical rotation is intimately tied to chirality and that it varies with chemical change.

• When (-)-malic acid reacts with PCl5, it produces (+)-chlorosuccinic acid.
• A further reaction with moist silver oxide yields (+)-malic acid.
• The reaction sequence that begins with (+) malic acid ends with (-) malic acid.

Walden Inversion Reaction Example

Walden Inversion Reaction Mechanism

In a chemical process, Walden’s inversion is the reversal of a chiral center in a molecule. Because a molecule can generate two enantiomers around a chiral center, the Walden inversion changes the molecule’s configuration from one enantiomeric form to another.

Walden inversion has a mechanism comparable to an SN₂ reaction. An intermediate is formed as a result of the nucleophilic assault on the carbon atom. This is followed by the displacement of the leaving group, which yields the product.

Video on Walden Inversion Reaction

References

• https://byjus.com/chemistry/walden-inversion/#
• https://www.vedantu.com/chemistry/walden-inversion
• https://testbook.com/chemistry/walden-inversion
• https://infinitylearn.com/surge/chemistry/walden-inversion/
• https://www.chemistrylearner.com/walden-inversion.html