In a Beta elimination reaction, the nucleophile attacks a\an:
Correct answer: B. Beta hydrogen
- A. Alpha hydrogen
- B. Beta hydrogen
- C. Hydrogen
- D. Alpha carbon
Explanation
The carbon, which has the halogen directly attached to it, is the alpha carbon and the adjacent carbon would be the beta carbon. The nucleophile, midst the reaction, strikes the hydrogen attached to the beta carbon, thus the beta hydrogen, removing it heterolytically. The bond pair, which is now a lone pair on the beta carbon, is used to form a pi bond between the alpha and the beta carbon. Hence the answer is B and the end product of the reaction is an alkene and a hydrogen halide.For E2 reactions, the halogen breaks off heterolytically, simultaneous to the formation of the pi bond. For E1 reactions, the halogen breaks off first leading to the formation of an alpha carbocation. The halide then proceeds by attacking the beta hydrogen and the rest is identical to the E2 process.
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About Alkyl Halides
Alkyl halides are named and related to their carbon-halogen structure, polarity and reactivity. The key reactions are nucleophilic substitution by SN1 and SN2 mechanisms and elimination by E1 and E2 mechanisms, including how substrate structure, nucleophile, base, solvent and temperature influence substitution versus elimination.
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