Dehydrohalogenation of secondary- and tertiary-alkyl halides proceeds by the preferential removal of the -hydrogen from the carbon that has the smallest number of hydrogens.
Originally formulated by A. Saytzeff (Zaitsev) to generalize the orientation in -elimination reactions of alkyl halides, this rule has been extended and modified, as follows:
Exceptions to the Saytzeff rule are exemplified by the Hofmann rule. SAYTZEFF (1875).
See also Markownikoff rule.