JEE Main · 2009 · 12 Apr 2009 · Offline · General Organic Chemistry

The alkene that exhibits geometrical isomerism is :

(A)propene
(B)2-methyl propene
(C)2-butene✓ Correct
(D)2- methyl -2- butene

Answer: (C)

Solution

Geometrical isomerism appears only when each carbon of the double bond carries two different groups, so that the arrangement across the bond cannot be flipped freely. But-2-ene,

C H_{3} CH = CHC H_{3}

, meets this requirement and exists as distinct cis and trans forms. Propene fails because one end of its double bond holds two hydrogens, and both 2-methylpropene and 2-methylbut-2-ene fail because one doubly bonded carbon carries two identical methyl groups.

JEE Main · 2009 · 12 Apr 2009 · Offline · Single correct option

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