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Topic: Determining absolute configuration for 3D structures  (Read 1040 times)

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Offline owlpower

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Determining absolute configuration for 3D structures
« on: November 25, 2018, 04:49:53 AM »
When assigning configurations to wedge and dash structures, they are simple because I can clearly see which atoms are in the front/back of the plane.

However, when given structures like these, which are more of a 3D field, I have trouble assigning the configuration.
There are 3 chiral centres here, and I have determined one to be S and the other to be R.
However, for the C marked with "*", I believe that it should be S because the ranking of the atoms are in anti-clockwise fashion (as seen in red).
There is another H connected to the C, which isn't drawn so I assume it's pointing downwards.

However, the answer given is R instead. Why is that so? Is the H atom not directed downwards for 3D structures like these?

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