Buprofen, a well-known non-steroidal anti-inflammatory drug, has chirality. Only the S enantiomer has anti-inflammatory activity (although the R enantiomer is converted slowly by the body into the S enantiomer). Add wedge-and-dash bonds to complete the perspective structures of the two stereoisomers of ibuprofen.

S structure = Wedge bond for CH3 and Dashed bond for H

R structure= Wedge bond for H and Dashed bond for CH3

Explanation:

First we have to identify the chiral carbon (figure 1) in the flat structure. The chiral carbon, in this case, is the one in which we have bonded the acid group, the methyl group, the hydrogen, and the benzene ring.

Then we have to assign the priorities if we want to know the absolute configuration of this carbon, therefore:

1 => Acid group

2=> Benzene group

3=> Methyl group

4=> Hydrogen

We have to remember that if we have fewer hydrogens in carbon we will have more importance. When we put the hydrogen with the dashed bond the number 4 priority (hydrogen) will be placed in the back therefore we can assign the configuration, in this case, we have a counterclockwise orientation. So, if we put H with the dashed bond, we will have an S configuration (figure 2).

If we want to find the "R" configuration we have to exchange the bonds between the CH3 group and the Hydrogen. When we do this, the number 4 priority will be placed in the front, therefore, we have to spin the molecule to put number 4 in the back when we do this we will obtain a clockwise orientation. So, if we put the H with the wedge bond, we will have an R configuration (figure 3).

c, liquids evaporate, creating a gas