Question: Which nitrogen atom in each compound is more basic?

a.

b.

4-(N,N-dimethylamino)pyridine contains two nitrogen atoms. Both the nitrogen atoms are sp² hybridized. The pyridine nitrogen does not participate in the delocalization of electrons but is attracted towards the ring.

The diethylamino nitrogen delocalizes its electrons in the ring. Therefore, DMAP is less basic.

Nicotine contains two nitrogen atoms. The pyridine nitrogen atom is sp² hybridized. The pyridine nitrogen does not participate in the delocalization of electrons but is attracted towards the ring.

The nitrogen atom in the five-membered ring is sp³ hybridized, which is free to donate its electrons. Therefore, nicotine is more basic.

a. The nicotine is more basic than DMAP.

In the DMAP, the N is also sp² hybridized but the electron pair occupies a p orbital so it can delocalize onto the aromatic ring. Delocalization makes this N less basic.

The nicotine is represented as:

Structure of DMAP

b. The more basic nitrogen is shown below:

Structure of nicotine