JEE Main · 2004 · 24 Apr 2004 · Offline · General Organic Chemistry

Which of the following will have meso-isomer also?

(A)2-chlorobutane
(B)2-hydroxyopanoic acid
(C)2,3-dichloropentane
(D)2-3-dichlorobutane✓ Correct

Answer: (D)

Solution

A meso compound needs two or more stereocentres yet an internal mirror plane that cancels the optical activity. 2,3-dichlorobutane,

CH X_{3} CHClCHClCH X_{3}

, has matching stereocentres at C-2 and C-3; the arrangement with the two chlorines on opposite faces carries a plane of symmetry down the middle and is the meso form. The other molecules lack this balanced pair of identical stereocentres, so only 2,3-dichlorobutane shows a meso isomer.

JEE Main · 2004 · 24 Apr 2004 · Offline · Single correct option

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