Q8 · CSIR NET Chemistry, December 2013
Paper: CSIR NET December 2013 · Subject: Organic Chemistry · Chapter: General Organic Chemistry · Topic: General Organic Chemistry – General · Marks: 2 · Difficulty: Medium
The two benzylic hydrogens $\mathrm{H_A}$ and $\mathrm{H_B}$ in the compounds I and II, are 
(I) (II)
(I) (II)(a)diastereotopic in I and enantiotopic in II
(b)diastereotopic in II and enantiotopic in I
(c)diastereotopic in both I and II
(d)enantiotopic in both I and II
Answer
Answer: B ✓ checked by 4AB · confidence high
Explanation
In I (cis-2,6-dimethyl, meso) the benzylic CH₂ lies on the mirror plane, so H_A/H_B are enantiotopic. In II (trans, chiral) there is no such symmetry, so they are diastereotopic (b).
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