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Zaitsev’s Rule

Zaitsev’s or Saytzev’s (anglicized spelling) rule is an empirical rule used to predict regioselectivity of 1,2-elimination reactions occurring via E1 mechanism or via E2 mechanism.  It states that in a regioselective E1 or E2 reaction the major product is the more stable alkene, i.e., the alkene with the more highly substituted double bond.

eg:



E1 reaction always follow Zaitsev’s rule; with E2 reactions, there are exceptions (see antiperiplanar).

see also Hofmann rule