The major product formed in the reaction of (2 R, 3 R)-2- bromo -3- methylpentane with NaOMe is: · ABC26IN0477

Subject: Inorganic Chemistry · Chapter: Main Group Elements · Topic: Main Group Element – General · Exam: GATE 2005-2021 · Marks: 2 · Difficulty: Medium

The major product formed in the reaction of $(2 \mathrm{R}, 3 \mathrm{R})-2-$ bromo $-3-$ methylpentane with NaOMe is:
(a)$(2 \mathrm{S}, 3 \mathrm{R})-2-$ methoxy $-3-$ methylpentane
(b)(Z)-3-methylpent-2-ene
(c)$(2 \mathrm{R}, 3 \mathrm{R})-2-$ methoxy $-3-$ methylpentane
(d)(E)-3-methyplent-2-ene
Answer
Answer: D ✓ checked by 4AB · confidence high

The source book printed no answer; this one was worked out and checked — see the explanation.

Explanation
NaOMe on a secondary bromide gives E2 (Zaitsev). Anti-periplanar elimination of H-3 and Br-2 from the (2R,3R) isomer places the C-2 methyl trans to the ethyl group, i.e. (E)-3-methylpent-2-ene.

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