Dehalogenation can be effected with many metals, e.g. zinc, magnesium, lithium and sodium in ammonia. Other reagents are sodium naphthalenide, phenyllithium, lithium aluminum hydride, chromium(II) chloride, sodium iodide, sodium sulfide and sodium selenide.
Usually good yields are obtained in these reactions; however, since the best route to the starting material is halogen addition to an alkene, the preparative value is limited. An advantage over dehydrohalogenation is the fixed position of the formed double bond.
The mechanisms of the dehalogenations are complex and depend on the particular conditions. The reactions are sometimes stereospecifically anti, but in other cases no stereospecificity has been observed.