What is the Saytzeff rule?

The Saytzeff rule, also known as Saytzev's rule or Zaitsev's rule, is a principle in organic chemistry that helps predict the favored product in elimination reactions. It states that in a dehydrohalogenation or dehydrating reaction, the major product will be the alkene with the more substituted double bond.

According to the Saytzeff rule, when a hydrogen halide (HX) is eliminated from an alkyl halide or an alcohol, the more substituted alkene is typically the major product. In other words, the hydrogen atom is removed from the β-carbon that has the greater number of hydrogen atoms attached to it, resulting in the formation of the more stable alkene.

The stability of an alkene is determined by the degree of substitution around the double bond. Alkenes with more alkyl groups attached to the carbon atoms of the double bond are considered more stable due to the increased electron-donating inductive effect and steric hindrance provided by the alkyl groups. Consequently, these more stable alkenes are generally the major products in elimination reactions.

It's important to note that the Saytzeff rule is a general guideline and may not always apply in every elimination reaction. In some cases, the reaction conditions or the presence of specific reagents can lead to the formation of less stable alkenes, which deviate from the predicted Saytzeff product.