Cyclohexane Ring Conformation - Question about convention??

[MDJerome]

---

Members do not see this ad.

I'm going over TPR and one of the example questions they ask is to determine which pair of "substituted cyclohexanes is the more stable isomer."

I'm confused about the convention for dashes and wedges. When drawing the chair conformation - Do I put the wedges up or down?

Organic Second Language said the convention is UP for wedges and DOWN for dashes. TPR seems to have done it the opposite way. Both ways resulted in entirely different answers and stabilities so if anyone knows how I approach this, it would be appreciated very much.

 

[kehlsh]

The wedges and dashes are a tool to help you see the structure in 3-dimensional way. Make sure you understand what those lines represent and be able to form a 3-D picture out of that. Then, no matter where wedges/dashes are located, you can form a strong conclusive answer.

 

[RogueUnicorn]

whether the wedge is up or down would depend on your perspective. drawn the standard way, though, both wedges and dashes are equatorial, which is to say both down AND up.

 

[MDJerome]

The wedges and dashes are a tool to help you see the structure in 3-dimensional way. Make sure you understand what those lines represent and be able to form a 3-D picture out of that. Then, no matter where wedges/dashes are located, you can form a strong conclusive answer.

I know what wedges and dashes mean but I'm just confused. This is what they suggest:

Anything coming off the ring that is on a wedge, we will call up, because the group is coming up above the ring. Any group on a dash, we will call down, because the group is going down below the ring.

However, TPR is saying "As a good rule of thumb, it's best to first put the bulkier substituent in a roomier equatorial position and decide if it's the more stable of the two chair conformations.

TPR method makes since considering substituted cyclohexanes would conform to the most stable position (with their largest groups in the equatorial position).

With these types of problems - do I just place the largest substituted groups in the equatorial position?

 

[Moosecakes]

I know what wedges and dashes mean but I'm just confused. This is what they suggest:



However, TPR is saying "As a good rule of thumb, it's best to first put the bulkier substituent in a roomier equatorial position and decide if it's the more stable of the two chair conformations.

TPR method makes since considering substituted cyclohexanes would conform to the most stable position (with their largest groups in the equatorial position).

With these types of problems - do I just place the largest substituted groups in the equatorial position?

That will give you the most stable conformation.