Quantcast

Can anyone please explain assignment of R,S on a Ring ? I need help.

This forum made possible through the generous support of SDN members, donors, and sponsors. Thank you.
Status
Not open for further replies.

cheesegirl

Full Member
10+ Year Member
Joined
Sep 20, 2006
Messages
127
Reaction score
0
The first step in assigning the absolute stereochemistry is to assign priorities to the groups attached to the chiral center. Higher priority is given to higher atomic number. Then rotate the structure so that the lowest priority group is away from you (into the plane of the screen). Then, determine whether the priorities for the other three groups descend in the clockwise or counterclockwise direction. If the group priorities are in a clockwise order, the chiral center is of R stereochemistry. If the priorities are counterclockwise, the center is S.

For the compound shown here, the highest priority group is the oxygen (red). The second highest priority group is nitrogen (blue). The third highest priority is carbon (grey), and the lowest priority group is hydrogen (white). With the hydrogen in back, the priorities are in a clockwise direction, so this compound has R stereochemistry.

http://web.centre.edu/muzyka/organic/jmol10/stereochemistry/RSjmol.htm (just google search it...)
 

braluk

SDN Surgerynator
Moderator Emeritus
10+ Year Member
5+ Year Member
Joined
Apr 30, 2006
Messages
11,823
Reaction score
68
Please do not post asking for help with homework assignments. Closing.
 
Status
Not open for further replies.
Top