Advantage of a wittig synthesis over dehydrohalogenation?
The Wittig reaction has become a popular method for alkene
synthesis precisely because of its wide applicability. Unlike
elimination reactions (such as dehydrohalogenation of alkyl
halides), which produce mixtures of alkene regioisomers determined
by Saytzeff's rule, the Wittig reaction forms the double bond in
one position with no ambiguity.