Zaitsev's Rule

Elimination reactions often can yield multiple products. However, not all of these products will be of equal stability. Zaitsev’s Rule (also spelled Saytzeff’s Rule) helps us predict the major product. 

Zaitsev vs. Hofmann Product

Zaitsev’s Rule predicts that in most cases, the most substituted product will be favored. This is also known as the Zaitsev product

The exception to this rule comes with the use of bulky bases. These promote the formation of the less substituted product.

  • The most common bulky bases are lithium diisopropylamide (LDA) and tert-butoxide (t-BuO-)

Thermodynamic vs. Kinetic Product

  • The Zaitsev product is also known as the thermodynamic product, since it is the one that releases the most free energy overall (most negative ΔG°).
  • The Hofmann product is also known as the kinetic product, since it is the one that overcomes the lowest activation energy (Ea). 

Practice

Problem: What is the major product of the reaction?

3m

Problem: What is the major product of the reaction?

2m

Problem: What is the major product of the reaction?

6m