Rank the conformers of 1,2,4-trimethylcyclohexane in order of decreasing stability,putting the most stable first.
A)I II III IV
B)III II IV I
C)III IV II I
D)I II IV III

Question

Rank the conformers of 1,2,4-trimethylcyclohexane in order of decreasing stability,putting the most stable first. 
A)I > II > III > IV 
B)III > II > IV > I 
C)III > IV > II > I 
D)I > II > IV > III

Quizplus · Accepted Answer

The most stable conformation is the equatorial one, with bulky groups in a staggered arrangement. Conformer III has both of the methyl groups in equatorial positions, making it the most stable. Conformer IV has both methyl groups in axial positions, making it the least stable. Conformers I and II have one methyl group in an axial position, making them less stable than III but more stable than IV. Among I and II, I is more stable because the bulky groups are anti to each other, in contrast to II where they are gauche to each other. Therefore, the correct order of stability is III > IV > II > I, or choice C.

Rank the Conformers of 1,2,4-Trimethylcyclohexane in Order of Decreasing Stability,putting