Hi, this is a sterechemistry problem. If you have a fisher projection problem with Ch3 at the top, Cl on the left, ethyl group on the right, and a CH double bonded to a CH2 (CH=CH2)on the bottom, it is an S nomenclature correct?
I figured out that Cl is 1st priority, and CH3 is 4th priority....but can you explain to me why the ethyl group is of higher priority than the CH=CH2?
Sure! In order to determine the priority of the substituents in a Fisher projection, we use a set of rules called the Cahn-Ingold-Prelog (CIP) rules. These rules assign priorities to substituents based on the atomic number of the atoms directly bonded to the stereocenter.
Here's how you can determine the priority of the ethyl group (C2H5) compared to the CH=CH2 group:
1. Identify the substituents directly attached to the stereocenter: In this case, the ethyl group (C2H5) and the CH=CH2 group.
2. Compare the atoms directly bonded to the stereocenter: In the ethyl group, there is a carbon atom (C) bonded to three hydrogen atoms (H). In the CH=CH2 group, there is a carbon atom (C) bonded to a hydrogen atom (H) and a carbon atom (C) bonded to two hydrogen atoms (H).
3. Apply the CIP rules to determine the priority: According to the CIP rules, we compare the atoms bonded to the stereocenter based on their atomic number. In this case, carbon (C) has a higher atomic number than hydrogen (H). Therefore, the ethyl group (C2H5) with three carbon atoms has a higher priority than the CH=CH2 group, which has only one carbon atom.
Therefore, the ethyl group is of higher priority than the CH=CH2 group. Based on this information, you can determine the stereochemistry using the R/S nomenclature.