It is explained by the fact that the transition state is structurally and energetically similar to the species nearest to it on the reaction path, a fact known as the Hammond postulate.
There are many situations where it does not hold, such as bimolecular elimination reactions in cyclic systems, because of the antiperiplanar arrangement of the carbon-hydrogen bond and the bond between the carbon and the leaving group, and the end product is known as the Hoffman product. It is explained by the fact that the transition state is structurally and energetically similar to the species nearest to it on the reaction path, a fact known as the Hammond postulate. FTP, identify this rule in olefin chemistry which states that beta-elimination of an alkyl halide generally yields the most highly substituted alkene.
There are many situations where it does not hold, such as bimolecular elimination reactions in cyclic systems, because of the antiperiplanar arrangement of the carbon-hydrogen bond and the bond between the carbon and the leaving group, and the end product is known as the Hoffman product.
Zaitsev’s Rule