I'm trying to find the R/S configuration of this molecule right here: Molecule structure

At first I tried to find the rotation and then reverse it (since H is pointing outwards), I got an S configuration (drawn poorly here):

First attempt

Then I tried to use the enantiomers method. I swapped the Br and the H then tried to find the configuration of the new molecule. And, I got an S configuration (of the resulting new molecule, which leads to the original having R configuration), which is not what I expected:

Second attempt

I don't know what I've done wrong here, the two attempts should lead to the same result (unless I've done something wrong). I tried looking up other R/S config examples using the enantiomers method (switching method) and what I've noticed is that the wedge and the dotted lines are right next to each other, like this for example:

enter image description here

While the molecule above has a straight (?) line in between:

enter image description here

So does that mean I can only switch groups when the wedge and the dotted lines are next to each other? Or was the first method wrong? Please kindly explain. Thank you.

Update 1 I've added a 3D visualization of the molecule. The big red ball is bromine, the gray medium-sized balls are carbon atoms, and the little white ones are hydrogens. I've marked the chiral center (green arrow pointing to it) for clarity. I've also rotated the molecule so that the bromine is pointing outwards.


  • 1
    $\begingroup$ Have you tried building a 3D model to make sure you have not mistakenly swapped the configuration? $\endgroup$
    – matt_black
    Oct 6, 2022 at 12:49
  • 5
    $\begingroup$ Just my two cents: the way your stereocenter is drawn seems to make it unassignable (it is ambiguous). With that perspective, you could have either two wedged bonds or two dashed bonds to form a tetrahedron. Both your assignments are correct but for different (and unattainable) carbon geometries. The angles are a mess. $\endgroup$ Oct 6, 2022 at 13:47
  • 1
    $\begingroup$ I agree, poor drawing! Make the carbon in question look like it is tetrahedral. In your first picture, move the dashed bromine pointing northeast to a position pointing northwest, and still dashed ,just above the bold hydrogen. Now you should have no problems in visualization. $\endgroup$
    – user55119
    Oct 6, 2022 at 19:53
  • 1
    $\begingroup$ As long as it keeps pointing inwards, yes. $\endgroup$ Oct 7, 2022 at 6:55
  • 1
    $\begingroup$ Follow Ivan's lead. I would tweek tha methyl group like this. You might be interested in this. $\endgroup$
    – user55119
    Oct 7, 2022 at 18:57


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