Saytzeff Rule

Abstract

The Saytzeff rule or Zaitsev rule predicts the regio‐selectivity of olefin formation by the elimination of secondary or tertiary alkyl halides, in which the proton is eliminated preferentially from the carbon bearing the smallest number of protons. The regioselectivity to give a more stable olefin is referred to as the Saytzeff regiospecificity, and the corresponding olefin is known as the Saytzeff product, or Zaitsev product. The unimolecular elimination such as the Chugaev reaction and the pyrolysis of esters in the liquid phase follow the Saytzeff rule. However, the Saytzeff rule does not apply in some of the cases. Furthermore, it has been reported that the steric effect during the elimination may also lead to the product obeying the Hofmann rule, as indicated by the increased ratio of 1‐/2‐olefin. This rule is very useful in predicting the regioselectivity of elimination.