Reaction of an alkyl halide with alcoholic potassium hydroxide gives mainly
Correct answer: D. an alkene, by elimination of hydrogen halide
- A. an alcohol
- B. an alkane
- C. a carboxylic acid
- D. an alkene, by elimination of hydrogen halide
Explanation
In ethanol the hydroxide ion acts as a base rather than as a nucleophile, removing a hydrogen from the carbon next to the one bearing the halogen, so a double bond forms and the hydrogen halide is eliminated. Heat favours this route as well. The contrast with aqueous conditions, which give the alcohol, is the essential comparison in this topic.
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About Elimination Reactions
Elimination reactions remove a leaving group and a hydrogen atom from adjacent carbon atoms to form an alkene. The topic covers dehydrohalogenation of alkyl halides, E1 and E2 mechanisms, the role of base, solvent and substrate structure, and Zaitsev orientation, which is often contrasted with substitution.
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