Question

Indicate the stereochemical configuration for the tetrahedral center.

1) R
2) S
3) Cannot be determined

Answer 1

The stereochemical configuration at a tetrahedral center is indicated by the R or S descriptors. Group priority is assigned based on atomic numbers, and the orientation of these groups determines the R or S configuration. If the lowest priority group is not pointing away, the configuration obtained after drawing the arrow must be reversed.

Step-by-step explanation:

To indicate the stereochemical configuration for a tetrahedral center, the R or S descriptors are used to describe the absolute configuration of the chiral center. Here is how you can determine the configuration:

1. Assign priority based on the atomic number of atoms attached to the chiral center. The higher the atomic number, the higher the priority.
2. If the lowest priority group (#4) is pointing away from the viewer, you can then draw an arrow from group #1 to #2 to #3. If the arrow moves in a clockwise direction, the configuration is R; if it moves counterclockwise, the configuration is S.
3. If group #4 is not pointing away from the viewer, first swap it with the group that is. Then, follow the same method for drawing the arrow and assigning the configuration, but reverse the assignment (clockwise becomes S, and counterclockwise becomes R).

Using this method, you can determine the configuration shown in Figure 3.3.5. Recall that R stands for 'rectus' (right) and S for 'sinister' (left), referring to the direction of the priority groups around the chiral center.