September 15, 2019, 03:02:19 AM
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Topic: A question about trisubstituted cyclohexane total strain energies  (Read 1535 times)

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Offline nupatel87

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So I am doing a practice exam for my organic chemistry exam and I came upon a question I am having a bit of trouble with. I have to make the two chair conformations for a trans-trisubstituted cyclohexane and then calculate the strain energies to determine which conformation is more stable. There is a Cl on Carbon 1 and a CH(CH3)2 on Carbon 4 that both face downward, and CH3 on Carbon 2 toward the upward face.

I understand how to draw the chair conformations, but how does one calculate the strain energies? I know the 1-3 diaxial strain energies and gauche strain and how they interact on mono/disubstituted cyclohexane chair conformations, but what is different on a trisubstitution?.

The answer keys state that the strains are 10.5 kj/mol for the normal chair and 9.6kj/mol for the ring flip. I calculated 7.6kj/mol and 7.2kj/mol for the ring flip.

Any idea on how to find out the energies? Thanks in advance. 

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