Identify all carbon chiral centers in coniine, nicotine, and cocaine.

Chiral centers are carbon atoms with four different groups attached to it by single bonds. A presence of chiral center will give raise to stereoisomers. When two stereoisomers are non superimposable mirror images of each other then they are called enantiomers.

In coniine, the carbon next to -NH group has four different groups (highlighted in red). In nicotine, a carbon in the five membered ring has four different groups.  In cocaine, two carbon atoms in the bicyclic ring has four different groups.