Li Hong (August 2014 Intake):
Just discovered something that might be beneficial to students, ON 13 P43 the “deadly” stereoisomers question, I find using RS notation useful, although not in the syllabus.
The configuration for FGHJ respectively are RS, SS, SR, RS
from there, we can deduce that F and J are identical
And the missing configuration which required in part III is of the RR configuration
i.e. We just copy the left side of F and right side of H which yields the answer.
Just sharing.
I think this is easier than picturing how the wedge and dashes change when it is rotated 60 and 120 degrees. It’s just dizzy to picture.

additional:
RS works quite well to be honest. Can loot at ON 14 there’s another similar question for stereoisomers.
Actually the real way to learn stereochemistry is to know RS, can’t fully understand it if we were to omit it. From RS, ten we can see why the maximum number of chiral compounds we have is 2^n, where n is the number of chiral centres.

Coincidentally, I was doing this paper last night, got stuck on this question as well. Thank you sir!

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Li Hong (August 2014 Intake):

Just discovered something that might be beneficial to students, ON 13 P43 the “deadly” stereoisomers question, I find using RS notation useful, although not in the syllabus.

The configuration for FGHJ respectively are RS, SS, SR, RS

from there, we can deduce that F and J are identical

And the missing configuration which required in part III is of the RR configuration

i.e. We just copy the left side of F and right side of H which yields the answer.

Just sharing.

I think this is easier than picturing how the wedge and dashes change when it is rotated 60 and 120 degrees. It’s just dizzy to picture.

additional:

RS works quite well to be honest. Can loot at ON 14 there’s another similar question for stereoisomers.

Actually the real way to learn stereochemistry is to know RS, can’t fully understand it if we were to omit it. From RS, ten we can see why the maximum number of chiral compounds we have is 2^n, where n is the number of chiral centres.

LikeLike