JEE Main · 2005 · 08 May 2005 · Offline · Haloalkanes and Haloarenes

Elimination of bromine from 2-bromobutane results in the formation of-

(A)equimolar mixture of 1 and 2-butene
(B)predominantly 2-butene✓ Correct
(C)predominantly 1-butene
(D)predominantly 2-butyne

Answer: (B)

Solution

Dehydrohalogenation of 2-bromobutane can strip a hydrogen from either side of the

C - Br

carbon, giving but-1-ene or but-2-ene. Saytzeff's rule tells us the more substituted, more stable alkene is favoured, and but-2-ene, with alkyl groups at both ends of the double bond and extra hyperconjugative stabilisation, is that product. So elimination gives predominantly 2-butene.

JEE Main · 2005 · 08 May 2005 · Offline · Single correct option

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