JEE Main · 2023 · 25 Jan 2023 · Shift 1 · General Organic Chemistry

Which of the following conformations will be the most stable?

(A)(see structure)
✓ Correct
(B)(see structure)
(C)(see structure)
(D)(see structure)

Answer: (A)

Solution

A Newman projection is lowest in energy when the bonds are staggered and the two bulky methyl groups are held as far apart as possible, that is anti to each other at a dihedral angle of

18 0^{\circ}

. Eclipsed projections raise the energy through torsional strain, and a gauche staggered form, with the methyls only

6 0^{\circ}

apart, suffers steric repulsion between them. The most stable arrangement is the staggered conformation with the two methyl groups anti.

JEE Main · 2023 · 25 Jan 2023 · Shift 1 · Single correct option

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