Zaytsev's rule

While at the University of Kazan, Russian chemist Alexander Zaytsev studied a variety of different elimination reactions and observed a general trend in the resulting alkenes.

[1] More generally, Zaytsev's rule predicts that in an elimination reaction the most substituted product will be the most stable, and therefore the most favored.

The rule makes no generalizations about the stereochemistry of the newly formed alkene, but only the regiochemistry of the elimination reaction.

[clarification needed] Alexander Zaytsev first published his observations regarding the products of elimination reactions in Justus Liebigs Annalen der Chemie in 1875.

[2][3] Although the paper contained some original research done by Zaytsev's students, it was largely a literature review and drew heavily upon previously published work.

Aleksandr Nikolaevich Popov published an empirical rule similar to Zaytsev's in 1872,[5] and presented his findings at the University of Kazan in 1873.

Zaytsev and Markovnikov both studied under Alexander Butlerov, taught at the University of Kazan during the same period, and were bitter rivals.

The removal of the proton and the loss of the leaving group occur in a single, concerted step to form a new double bond.

[9] Due to steric interactions, a bulky base – such as potassium tert-butoxide, triethylamine, or 2,6-lutidine – cannot readily abstract the proton that would lead to the Zaytsev product.

These intramolecular interactions are relevant to the distribution of products in the Hofmann elimination reaction, which converts amines to alkenes.

For example, when menthyl chloride is treated with sodium ethoxide, the Hofmann product is formed exclusively,[13] but in very low yield:[14] This result is due to the stereochemistry of the starting material.

E2 eliminations require anti-periplanar geometry, in which the proton and leaving group lie on opposite sides of the C-C bond, but in the same plane.