The alcoholate-induced dehydrochlorination of styryl chloride possibly occurs by the 3 different competing mechanisms: E2, E1cb, and E1cb-HBA an E1cb modification. These conclusions were confirmed by H-D exchange, isotope effects, order of reaction, and relative elimination rates as a function of the cis or trans configuration of the material and of the nature of the base (EtONa or tert-BuOK.) [on SciFinder (R)]