SME
Organic Chemistry I · Problem type
CIP priority: rank the groups
Use this for “Rank –CH₃, –OH, –H and –CH₂OH by Cahn–Ingold–Prelog priority, highest first.”
Put in order
Order by CIP priority, highest first.
1
?
2
?
3
?
4
?
5
?
6
?
Assumptions
•
Look first at the atom joined to the stereocenter: the higher its atomic number, the higher the priority. Br is 35, O 8, N 7, C 6 and H 1.
•
When those atoms tie, list the three atoms on each and compare them, highest first, until one list wins: –CH₂OH has (O, H, H) and –CH₃ has (H, H, H).
•
A double bond counts its atom twice, so –CH=O reads as (O, O, H).
Topic check
See what you know: 5 questions on this topic
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