Saytzeffs

Saytzeffs, also known as Saytzeff's rule or Zaitsev's rule, is an empirical rule in organic chemistry that describes the regioselectivity of elimination reactions. It states that in an elimination reaction, the more substituted alkene is typically the major product. The substitution refers to the number of carbon atoms directly attached to the carbons involved in the double bond. For example, if an elimination reaction can produce both a disubstituted alkene and a monosubstituted alkene, Saytzeff's rule predicts that the disubstituted alkene will be formed in greater yield. This is generally attributed to the greater thermodynamic stability of more substituted alkenes.

Saytzeff's rule is most commonly applied to E1 and E2 elimination reactions. In E1 reactions, where a carbocation intermediate is formed, the more substituted carbocation is more stable, leading to the formation of the more substituted alkene. In E2 reactions, the transition state leading to the more substituted alkene is often more stable due to hyperconjugation. However, it is important to note that Saytzeff's rule is a prediction and not an absolute law. Steric hindrance from bulky bases or substrates can sometimes favor the formation of the less substituted alkene, known as the Hofmann product, which is then referred to as Hofmann elimination.

The rule was named after the Russian chemist Aleksandr Butlerov, who first described the principle, and later expanded upon by his student, Aleksandr Saytzeff. Understanding Saytzeff's rule is crucial for predicting the products of elimination reactions in organic synthesis and for mechanistic studies.