# Newman projections: how to tell which groups are bulkiest to determine what is the most stable conformation?

### The scenario

Let's say we have a molecule where in the Newman projection the front carbon has a hydrogen, methyl and an ethyl, and in the back carbon there's a hydrogen, something like a S, Cl or Br (bigger than carbon but only one atom), and something like another ethyl or isopropyl:

### My understanding

Methyls/ethyls/isopropyls etc. would cause more steric hindrance than something like S, Cl or Br because they consist of multiple atoms and take up more space, so in the scenario above, the front carbon's ethyl should be 180° away from the back carbon's ethyl/isopropyl, and the S/Cl/Br's position would be dependent on the ethyl from rotation. I think the following should be the most stable conformation:

### My question

I've seen some similar examples where (in the same type of scenario) the S/Cl/Br was considered "bulkier" and was put 180° away from a big isopropyl, when something like an ethyl could have been there instead, but was put only 60° away from the big isopropyl (see the first illustration). I'm not sure if these examples were just wrong or if I'm completely misunderstanding how to determine what's bulkiest, so any advice on how to determine that would be super. If a table that ranks most-to-least bulkiest exists, please share.

So, the $$\ce{-SH}$$,$$\ce{-Cl}$$ and $$\ce{-Br}$$ groups seem to be less hindering than the $$\ce{-iPr}$$ group.