ConfusedOne

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This is a question from topscore. What would the absolute configuration of this be? R or S? Thanks

....Br
.....|
F--C--CHO
.....|
.....H

please ignore periods
 

keibee82

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ConfusedOne said:
This is a question from topscore. What would the absolute configuration of this be? R or S? Thanks

....Br
.....|
F--C--CHO
.....|
.....H

please ignore periods

S
 
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ConfusedOne

ConfusedOne

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yeah thanks. My mind must be jello from all this studying. For some reason I thought F gets the priority :laugh:
 

Envision

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ConfusedOne said:
yeah thanks. My mind must be jello from all this studying. For some reason I thought F gets the priority :laugh:
Probably bc F is the most electronegative. however, for R/S config. highest priority is given the atom with the highest atomic number.
 

dat_student

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allstardentist said:
hey how do u guys know if the hydrogen is pointing out of the screen or into the screen based on what he has shown? just assumed that hydrogen is pointing into the screen?
Don't worry about that.

1st put the lowest priority at the top.
....Br
.....|
F--C--CHO
.....|
.....H

....H
.....|
F--C--Br
.....|
.....CHO

Br (1)-->F(2)-->CHO(3) is counter clockwise. So it's S

P.S. There is a faster way.
 

dat_student

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allstardentist said:
also i dont understand how u got from the first structure to the second one. can u explain how u got that? thanks.
keep one stationary and rotate the other three clockwise OR counter clockwise.

allstardentist said:
oh wait, that is in fischer projection? and whats the faster way?
it's been a while. you have to double check me.

faster way:

if lowest priority is at top or bottom. Look at the other three if clockwise R if counter S

if lowest p. right or left clockwise is S, counter c. is R

(faster because you don't have to put the lowest priority group at the top)

Like I said, it's been a while. you'll have to double check.
 
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