Which products are formed when a haloalkane undergoes dehydrohalogenation with a base?

Master NCEA Level 3 Organic Chemistry Reaction Schemes. Prepare with multiple choice questions, complete with hints and detailed explanations. Ace your exam with our comprehensive tools!

Multiple Choice

Which products are formed when a haloalkane undergoes dehydrohalogenation with a base?

Elimination of a haloalkane with a base is an E2-type process: the base grabs a proton on the carbon next to the one bearing the halogen, and the carbon–halogen bond breaks at the same time to form a double bond. The halide leaves as X–, so the byproduct is hydrogen halide (HX). This means the organic product is an alkene, and the inorganic/byproduct is HX. That’s why the correct description is alkene plus HX. Substitution pathways would give an alcohol, and forming a diol would require two additions or substitutions, not a single elimination.

Elimination of a haloalkane with a base is an E2-type process: the base grabs a proton on the carbon next to the one bearing the halogen, and the carbon–halogen bond breaks at the same time to form a double bond. The halide leaves as X–, so the byproduct is hydrogen halide (HX). This means the organic product is an alkene, and the inorganic/byproduct is HX. That’s why the correct description is alkene plus HX. Substitution pathways would give an alcohol, and forming a diol would require two additions or substitutions, not a single elimination.

More practice questions