[ilikecats]

hey everyone,

so im in my first year of organic chemistry

in my homework i have a question
"Draw the most stable conformation of cis-1,2-dimethylcyclohexane"

heres what i did:



i know equatorial means more stable, and in both conformations, theres 1 equatorial, and one axial, and both CH3, same value. so aren't these degenerate?
apparently its the 1st one though...how come? i keep searching but i dont know



im sorry if this is super easy...im just a tiny first year college student!

[Archer]

Do you have a molecular modelling kit? (not software, althoug this is better than nothing), sometime holding a molecular structure in your hands can be very helpful in understanding these.

It looks to me like you have draw two identical conformations but rotated one and numbered the carbons differently.

Is this the only conformation which the ring can adopt?

[Babcock_Hall]

I agree.

[spirochete]

If somebody asked you to draw the more stable chair conformation than it was a poorly worded question. Technically in this case the two chair conformations are different because they are mirror images. Mirror images have the same energy, of course, so you cannot pick which one is more stable.

[Vidya]

hey everyone,

so im in my first year of organic chemistry

in my homework i have a question
"Draw the most stable conformation of cis-1,2-dimethylcyclohexane"

heres what i did:



i know equatorial means more stable, and in both conformations, theres 1 equatorial, and one axial, and both CH3, same value. so aren't these degenerate?
apparently its the 1st one though...how come? i keep searching but i dont know



im sorry if this is super easy...im just a tiny first year college student!

This is the only conformation for the molecule mentioned by you.

[Archer]

hey everyone,

so im in my first year of organic chemistry

in my homework i have a question
"Draw the most stable conformation of cis-1,2-dimethylcyclohexane"

heres what i did:

i know equatorial means more stable, and in both conformations, theres 1 equatorial, and one axial, and both CH3, same value. so aren't these degenerate?
apparently its the 1st one though...how come? i keep searching but i dont know



im sorry if this is super easy...im just a tiny first year college student!

This is the only conformation for the molecule mentioned by you.

No, cis-1,2-dimethylcyclohexane can form other conformations and I was trying to prompt the OP to come up with them.

[Vidya]

cis-1,2-dimethylcyclohexane"
this has only one conformation

[Dan]

cis-1,2-dimethylcyclohexane"
this has only one conformation

No, it has one chair conformation - there are others.

[orgopete]

hey everyone,

so im in my first year of organic chemistry

in my homework i have a question
"Draw the most stable conformation of cis-1,2-dimethylcyclohexane"

i know equatorial means more stable, and in both conformations, theres 1 equatorial, and one axial, and both CH3, same value. so aren't these degenerate?
apparently its the 1st one though...how come? i keep searching but i dont know.

Re: degenerate
Yes, they are degenerate. I'm assuming this was you question (because it is what was asked). Although looking at the chair conformations may seem as though they could be mirror images, cis-1,2-dimethylcyclohexane is a meso compound, the isomers are the same compound. If so, that may explain why it's the first compound.

In this case, the wedged representation makes it easier to note the symmetry than the chair, which will appear to have a mirror image structure. Flipping the mirror image will give a the same structure back.

I hope I have answered what I think you were trying to understand.

[Archer]

cis-1,2-dimethylcyclohexane"
this has only one conformation

I think you need to read up on what a conformation is before you make statements like this.

[spirochete]

hey everyone,

so im in my first year of organic chemistry

in my homework i have a question
"Draw the most stable conformation of cis-1,2-dimethylcyclohexane"

i know equatorial means more stable, and in both conformations, theres 1 equatorial, and one axial, and both CH3, same value. so aren't these degenerate?
apparently its the 1st one though...how come? i keep searching but i dont know.

Re: degenerate
Yes, they are degenerate. I'm assuming this was you question (because it is what was asked). Although looking at the chair conformations may seem as though they could be mirror images, cis-1,2-dimethylcyclohexane is a meso compound, the isomers are the same compound. If so, that may explain why it's the first compound.

In this case, the wedged representation makes it easier to note the symmetry than the chair, which will appear to have a mirror image structure. Flipping the mirror image will give a the same structure back.

I hope I have answered what I think you were trying to understand.

The chair conformations of this molecule are chiral. It is not uncommon for achiral molecules to have chiral conformations. These types of molecules must exist as rapidly equilibrating racemic mixtures. Thus they lack optical activity and are considered achiral. This is a minor point that is rarely talked about in sophomore level classes but is frequently in sophomore level textbooks. Some achiral chair compounds do have achiral chair conformations which are absolutely identical, such as the cis 1,3 variant.

Orgopete is correct in the sense that it usually best to draw a molecule in it's most symmetrical conformation when making a determination about chirality, even if the molecule barely or never even exists as the conformation you're drawing. This is true of chairs. It doesn't work so well with other examples such as certain biaryl compounds.

[spirochete]

Explanation here: http://www.utdallas.edu/~scortes/ochem/OChem1_Lecture/Class_Materials/09_stereo_notes.pdf

This is beyond what the original poster probably wants or needs but I know other people read these threads also.