Zaitsev's Rule (or Saytzeff's Rule) is an empirical rule for predicting the favored alkene product(s) in elimination reactions. While at the University of Kazan, Russian chemist Alexander Zaitsev studied a variety of different elimination reactions and observed a general trend in the resulting alkenes. Based on this trend, Zaitsev stated, "The alkene formed in greatest amount is the one that corresponds to removal of the hydrogen from the β-carbon having the fewest hydrogen substituents." For example, when 2-iodobutane is treated with alcoholic KOH, 2-butene is the major product and 1-butene is the minor product.
More generally, Zaitsev's rule predicts that in an elimination reaction, the most stable alkene - typically the most substituted one - will be the favored product. While effective at predicting the favored product for many elimination reactions, Zaitsev's rule is subject to many exceptions.
Read more about Zaitsev's Rule: History, Thermodynamic Considerations
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