Which Wedge-and-dash Drawing Correctly Represents The Chair Conformation Given?

In the previous ii posts, we have talked virtually drawing the ring-flip of chair conformations and the A value (1,3-diaxial interactions). And nosotros learned that for a given cyclohexane, the axial conformer is less stable than the corresponding equatorial conformer. For instance, the energy divergence of the axial and equatorial isopropyl cyclohexane is ix.two kJ/mol.

So, choosing the more stable chair conformation is straightforward when in that location is only one group on the cyclohexane. You just need to find the energy value for the axial grouping:

However, if there are more than groups on the cyclohexane, we demand to take into consideration the ane,3-diaxial interaction of all.

Case: what is the most stable chair conformation of the following substituted cyclohexane?

To answer this question, we need to draw the two chair conformations and compare the energies of all the axial groups on each conformer.

1. Number the ring and draw any chair conformation of the compound:

two. Draw the second chair conformation (ring-flip-cheque this post if non certain):

And now the stabilities: For each chair conformer, add the energy of all the groups on axial position.

In the showtime conformer, nosotros have two chlorines in axial positions, and so the total steric strain is:

2.2+2.2 = 4.4 kJ

For the 2d conformer, the chlorines at present are equatorial, and nosotros only have i methyl group in axial position. Therefore, the energy is 7.three kJ/mol.

Out of 2 conformations, the 1 with lower free energy is more stable. And then, despite having two axial groups, the showtime conformer is more as two chlorines do not bring as much steric interaction as the methyl group.

Draw both chair conformation (ring-flip) and use the table to calculate the relative free energy toll associated with each group in the centric position to determine the more than stable chair conformation of each of the following compounds:

answer

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Solution

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