Zaitsev's rule

Zaitsev's rule (or Saytseff's rule, Saytzev 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 ß-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.