Question

The following structures are optically active compounds. Star (*) the asymmetric carbon atoms in these structures.

Short answer

When four different atoms or groups are attached to the central carbon atom, it is known as asymmetric carbon. The chirality of a structure can be predicted by the presence of an asymmetric center. Though an asymmetric carbon atom is a very important aspect in determining the chirality of a molecule, it is not the only factor determining chirality. Several ring structures also show axial chirality.

Step-by-step solution

Asymmetric carbon

When four different atoms or groups are attached to the central carbon atom, it is known as asymmetric carbon. The chirality of a structure can be predicted by the presence of an asymmetric center. Though an asymmetric carbon atom is a very important aspect in determining the chirality of a molecule, it is not the only factor determining chirality. Several ring structures also show axial chirality.

Asymmetric center of the first structure

The asymmetric carbon is marked with an asterisk.

Both structure a and b represent the same molecule. Structure b gives more clarity as it shows that the central carbon is bonded to four different groups. The four different groups are : CH₂Br, NH₂, CF₃ and

Asymmetric centre of the second structure’

This structure has two asymmetric carbons marked with asterisk.

Asymmetric center of the third structure

This structure has three asymmetric carbons marked with asterisk.

Asymmetric center of the fourth structure

This structure has three asymmetric carbons marked with asterisk.