[BoopBoopsInABowl]

Hi! First time posting but I've had this problem for the longest time that I do not know how to solve.

The first step of the problem was to add bromine to the alkene, which I've already done. The part that I've completed is shown below.



The issue that I have is that I do not know how to assign R and S to the compound above. I know the lowest carbon (the carbon in the methyl group opposite the side with the bromines) is a chirality center (since my teacher states it is), but as I try to assign priorities, I end up going down the ring and keep on getting stuck. I can assign R and S pretty easily, but not to ringed compounds that keep on ending up in ties or branching. For example, we had to assign R and S to alpha-pinene and I got stuck on that as well. I want to know in general and on this specific question, what is the way to assign chirality for these molecules.

[BoopBoopsInABowl]

I'm not exactly sure how to edit my post, so I'll reply with a followup.

The original structure that I had to add the bromine to is:



I'm not exactly sure how to assign the chirality of that either. My teacher says that in addition to E/Z isomerism, we can assign a chirality center to the carbon containing the methyl group opposite the double bond. Help would be appreciated!

[Dan]

The issue that I have is that I do not know how to assign R and S to the compound above.

You have not indicated any stereochemistry (using dashes/wedges). Without that, you cannot assign descriptors.

I know the lowest carbon (the carbon in the methyl group opposite the side with the bromines) is a chirality center (since my teacher states it is), but as I try to assign priorities, I end up going down the ring and keep on getting stuck.

This is a pseudoasymmetric centre (as is the the opposite C-Br), and can be assigned r/s (note the lower case - not R/S). The process is somewhat complicated and involves the use of auxiliary descriptors, you can read about it in this document, p28. Have a go.

I can assign R and S pretty easily, but not to ringed compounds that keep on ending up in ties or branching. For example, we had to assign R and S to alpha-pinene and I got stuck on that as well. I want to know in general and on this specific question, what is the way to assign chirality for these molecules.

α-Pinene is different from this case - it does not contain pseudoasymmetric centres, only "normal" asymmetric centres (or chiral centres). You should be able to follow the same process you would for a linear molecule.

The original structure that I had to add the bromine to is:



I'm not exactly sure how to assign the chirality of that either. My teacher says that in addition to E/Z isomerism, we can assign a chirality center to the carbon containing the methyl group opposite the double bond. Help would be appreciated!

In this case I think you need to assign axial chirality to the molecule as a whole (R_a/S_a or P/M) - see p32 of the document linked above.

I guess you could also do an E/Z and R/S assignment using auxiliary stereodescriptors - maybe that is what your teacher is getting at.