# Chapter 7 - Configurations - 7.7 Drawing Fischer Projections - Problems - Page 163: 7.78

The configuration of the stereocenter is "R". The enantiomer will have the same groups on the top and on the bottom, but the left group will be (OH) and the right group will be (H).

#### Work Step by Step

1. Draw wedges in the horizontal lines, and dashes on the vertical lines. 2. Now we have to choose one wedge and one dash to switch to "normal" bonds. - I will choose the Hydrogen and the top group (-CHO). 3. Determine the configuration of this stereocenter: - Determine the numbers that each group will get. - Hydroxyl (1), "CHO" (2), "$CH_2OH$" (3), Hydrogen (4). - We will have to use the switch method. - Switch the Hydrogen with the group on the wedge ($CH_2OH$) - Now, analyzing the new compound: - The numbers are increasing on the counterclockwise direction. - Which means that this compound is "S". - But, this compound is not the original one, we have switched two groups. - Therefore, the configuration of the original compound is the opposite: "R". 4. To draw the enantiomer, redraw the molecule and just switch the left groups with the right groups.

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