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Dehydrohalogenation is an organic chemistry reaction from which an alkene is obtained from an alkyl halide. It is also called the β-Elimination reaction. Ethanolic potassium hydroxide when reacted with alkyl halide gives alkene.
In this reaction, the halogen on the carbon in the alkyl halide reacts with hydrogen present on the β-carbon releasing hydrogen chloride. Hence an alkene is formed due to formation of a double bond between the α- and β-carbon.
Additional recommended knowledge
Chlorobenzene does not react with potassium hydroxide due to the presence of the benzene ring which provides too strong of a substrate for conventional elimination.
In general, the above reaction of haloalkane with potassium hydroxide would compete with an Sn2 nucleophilic substitution reaction (minor product) because OH- is a strong, sterically unhindered nucleophile. Perhaps a better reagent would be a deprotonated alcohol such as potassium tert-Butoxide ([CH3]3CO+ K-) or because it is an oxide anion and thus a strong base and nucleophile, potassium ethoxide (CH3CH2O+ K-) and because of steric hindrance therefore promoting an elimination mechanism instead of a substitution mechanism. Also, providing heat for the reaction to progress would further promote elimination.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Dehydrohalogenation". A list of authors is available in Wikipedia.|