These form part of a pattern first
observed by Russian chemist, Alexander Zaitsev (also pronounced as
Saytzeff) who in 1875 formulated a rule which can be summarised as
“in dehydrohalogenation reactions, the preferred product is that
alkene which has the greater number of alkyl groups attached to the
doubly bonded carbon atoms ” Thus, 2-bromopentane gives
pent-2-ene as the major product 3 Reaction with metals
Most organic chlorides, bromides and iodides react with certain
metals to give compounds containing carbon-metal bonds