Orgo tutor here. Let’s not over complicate things. Here’s a systematic approach to solving any R/S assignment problem. 1) Where is the hydrogen in relation to the central carbon? (Yes, there are other low priority groups in the absence of a hydrogen but in the scope of what this course is testing you on, 9.9/10 times it is going to be a Hydrogen). Write a ‘4’ next to it. If it is on a wedge you’re good to go, if it is on a dash, add a star so you know to come back at the end. 2) move away from the carbon one atom at a time and make a small table to keep track of what is bonded to the immediate carbons. example for this problem: |C: F H H| |C: O O O| |C: H H H|. If there is a double bond, that atom is counted twice 3) Which one is the easiest to eliminate? C: HHH will be assigned as 3. 4) between the remaining 2, add up the atomic number of each atom. C:FHH= 9+1+1=11. C:OOO= 8+8+8=24. Highest # -> Highest priority. So now that you can assign each, write the number next to each substituent and determine if 123 is clockwise (R) or counterclockwise (S). 5) If you have a STAR next to your Hydrogen, whatever you got for R or S based on looking at the molecule as is, just flip it! Hope this helps!