JEE Main · 2010 · 11 Apr 2010 · Offline · General Organic Chemistry

Out of the following, the alkene that exhibits optical isomerism is

(A)3-methyl-2-pentene
(B)4-methyl-1-pentene
(C)3-methyl-1-pentene✓ Correct
(D)2-methyl-2-pentene

Answer: (C)

Solution

Optical isomerism needs a carbon bearing four different groups. In 3-methyl-1-pentene,

C H_{2} = CH - CH (C H_{3}) - C H_{2} C H_{3}

, the third carbon carries a vinyl group, a methyl group, an ethyl group and a hydrogen, four different groups, so it is a stereocentre and the molecule is optically active. In the other alkenes the corresponding carbon repeats a group or lies on the double bond, so none is chiral; only 3-methyl-1-pentene shows optical isomerism.

JEE Main · 2010 · 11 Apr 2010 · Offline · Single correct option

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